Forecast Discussions mentioning "ACARS", "MDCRS", "AIRCRAFT", "TAMDAR", or "AMDAR" received at FSL on 01/13/07

.SYNOPSIS...A COLD UPPER LEVEL TROUGH WILL REMAIN OVER SOUTHERN CALIFORNIA THROUGH SATURDAY MORNING. UNSTABLE AIR OVER THE COASTAL WATERS TONIGHT AND NORTHERLY WINDS AGAINST THE MOUNTAIN SLOPES WILL CONTINUE TO GENERATE ISOLATED SHOWERS TONIGHT. RAIN AND SNOW AMOUNTS ARE EXPECTED TO BE LIGHT. SNOW MAY ACCUMULATE ON THE GROUND AT ELEVATIONS ABOVE 1000 FEET...BUT AMOUNTS SHOULD BE LESS THAN AN INCH. HIGH PRESSURE BUILDING OVER NEVADA WILL CAUSE GUSTY NORTHEAST WINDS THIS WEEKEND THROUGH THE PASSES AND CANYONS. TEMPERATURES WILL BE EXTREMELY COLD OVER THE WEEKEND AND FREEZE WARNINGS AND FROST ADVISORIES ARE IN EFFECT. WARMER TEMPERATURES WILL BEGIN MONDAY BUT SO WILL STRONG NORTHEAST WINDS AND A FIRE WEATHER WATCH HAS BEEN ISSUED FOR MOST OF NEXT WEEK.

&&

.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES...

AIR MASS STARTING TO DESTABILIZE NOW THAT THE TEMPORARY RIDGING BEHIND THIS MORNINGS SHORT WAVE IS ENDING AND GROUND TEMPERATURES HEAT UP. TONIGHT INSTABILITY WILL CONTINUE DUE TO THE RELATIVELY WARM POOL OF OCEAN WATER AND THE OVERLAYING COLD AIR CREATING UNSTABLE LAPSE RATES. NORTHWEST TRAJECTORIES ACROSS THE SOUTHERN CALIFORNIA BIGHT TONIGHT SHOULD GENERATE CONVERGENCE IN THE WAKE OF THE ISLANDS WHICH IN TURNS PROVIDES A LIFTING MECHANISM FOR GENERATING SHOWERS THAT ARE IN TURN CARRIED ONSHORE. MODEL SOUNDINGS SHOW PRECIPITABLE WATER AMOUNTS JUST OFFSHORE TONIGHT TO BE A QUARTER OF AN INCH OR LESS...ABOUT HALF OF WHAT THEY WERE THIS MORNING...SO WILL ASSUME THAT IS THE UPPER LIMIT OF ADDITIONAL PRECIPITATION FOR TONIGHT...BUT AM FORECASTING MUCH LESS...GENERALLY A FEW HUNDREDTHS FOR RAINFALL AND ONE INCH OR LESS FOR SNOWFALL. BECAUSE FREEZING LEVEL IS EXPECTED TO VERY LOW...EVENTUALLY REACHING THE SURFACE JUST ABOUT EVERYWHERE TONIGHT...ANY PRECIPITATION MAY BE IN THE FORM OF SNOW GRAINS/FLURRIES FOR THE MOST PART TONIGHT WITH ICE/SNOW PELLETS IN THE HEAVIER SHOWERS. STILL THREAT OF UPSLOPE CONDITIONS OVER MOUNTAINS...MAINLY NORTH AND NORTHWEST SLOPES TONIGHT SINCE THE UPPER TROUGH AXIS REMAINS OVER US INTO SATURDAY MORNING. VERY COLD DRY AIR MASS REMAINS IN PLACE THIS WEEKEND WITH LITTLE MODIFICATION EXPECTED. TEMPERATURES SATURDAY NIGHT MAY BE THE COLDEST DUE TO LESS WIND. SUNDAY NIGHT EXPECTED TO BE SIMILAR...THOUGH WINDS WILL BE INCREASING DUE TO INCREASING OFFSHORE PRESSURE GRADIENTS. ADJUSTED TEMPERATURES...HUMIDITY...AND WIND SATURDAY THROUGH THURSDAY. &&

.AVIATION... LATE MORNING ACARS SOUNDINGS INDICATE THE MARINE LAYER HAD BEEN WIPED OUT OVER THE AREA. MOST AREAS HAVE CLEARED OR SCATTERED OUT OVER THE AREA EXCEPT FOR SOME BROKEN CONDITIONS OVER THE MOUNTAINS AND PORTIONS OF THE EASTERN DESERTS BUT THESE AREAS SHOULD SCATTER OUT DURING THE REMAINDER OF THE AFTERNOON. EXPECT VFR CONDITIONS EVERYWHERE TONIGHT AND SATURDAY WITH A MOSTLY CLEAR SKY AND UNRESTRICTED VISIBILITIES.

MAIN PROBLEM FOR AVIATION WILL BE THE STRONG WEST TO NORTHWEST WINDS ACROSS THE MOUNTAINS THAT COULD PRODUCE SOME MOUNTAIN WAVE/ROTOR ACTIVITY ALONG THE LEE SIDE OF THE MOUNTAINS OVER THE COACHELLA VALLEY NEAR KPSP THROUGH THIS EVENING. THE WINDS ARE EXPECTED TO BECOME NORTH TO NORTHEAST TONIGHT AND SATURDAY WITH THE MOUNTAIN WAVE/ROTOR MOVING TO THE LEE SIDE OF THE SAN BERNARDINO MOUNTAINS NEAR KONT AND KSBD SATURDAY MORNING.

&&

.MARINE... GUSTY NORTHWEST WINDS 15 TO 25 KNOTS OVER THE COASTAL WATERS WILL DIMINISH THIS EVENING. THE SMALL CRAFT ADVISORY WILL REMAIN IN EFFECT THROUGH THIS EVENING.

&&

.SGX WATCHES/WARNINGS/ADVISORIES...

WIND ADVISORY FOR THE MOUNTAINS AND DESERTS THROUGH 8 PM. SEE LAXNPWSGX.

WIND CHILL ADVISORY TONIGHT...SAN BERNARDINO MOUNTAINS TO BE ISSUED AROUND 2 PM THIS AFTERNOON.

FROST ADVISORY LATE TONIGHT/SATURDAY MORNING...COASTAL SECTIONS...SAN DIEGO COUNTY DESERT.

FREEZE WARNING LATE TONIGHT/SATURDAY MORNING...INLAND EMPIRE...SN DIEGO COUNTY INLAND VALLEYS...AND COACHELLA VALLEY.

SMALL CRAFT ADVISORY THROUGH THE EVENING. SEE LAXCWFSGX.

HIGH RIP CURRENT RISK TODAY. SEE LAXSRFSGX.

FREEZE WATCH FOR THE INLAND VALLEYS AND LOWER DESERTS FROM SAT EVENING THROUGH MON MORNING. SEE LAXNPWSGX.

FIRE WEATHER WATCH SUNDAY NIGHT THROUGH THURSDAY...INLAND VALLEYS AND MOUNTAINS. SEE LAXRFWSGX.

$$

PUBLIC/FIRE WEATHER...BALFOUR AVIATION/MARINE.......HORTON

.EVENING UPDATE...

ZFP/GRIDS/WSW OUT. FOCUS OF THIS UPDATE WAS ON RAIN FALLING ACROSS SOUTHERN CWA. CALLS TO LIVINGSTON...FORD...AND LA SALLE COUNTY IN THE PAST HR OR SO INDICATE NO ICING PROBLEMS. PNT/TIP/IKK STILL ABOVE FREEZING AND REPORTING RAIN. COLD AIR WILL SLOWLY SINK SOUTH AND EXPECT RAIN TO SLOWLY CHANGEOVER TO FREEZING RAIN EVENTUALLY. BUT BY THE TIME IT DOES MAKE A CHANGE...QPF AMOUNTS WILL BE LIGHT. INDICATED UP TO ONE TENTH OF AN INCH OF ICE IN THE WSW ACROSS THIS AREA...BUT THIS WILL BE ISOLATED. WITH CHANGEOVER OCCURRING LATER... PUSHED FREEZING RAIN ADVISORY TO 12Z ACROSS THE SOUTHERN HALF OR SO OF THE CWA.

FURTHER NORTH...ADVISORY EXPIRED FOR NW IL AND THAT LOOKS ON TRACK. WAS RELUCTANT TO PULL ADVISORY FOR NE IL THOUGH AREAS NORTH OF I-88 APPEAR TO STAY MAINLY DRY THRU THE NIGHT. THOUGH ORD IS REPORTING -DZ THIS HR AND -RA AT MDW. WHILE SFC TEMPS REMAIN ABOVE FREEZING HERE...TEMPS COULD DIP BELOW FREEZING BEFORE 2AM. SINCE THE ADVISORY WAS ALREADY OUT...DECIDED TO LET IT RIDE FOR NOW...BUT PRECIP WILL BE LIGHT AND IMPACTS SHOULD BE SMALL.

&&

.DISCUSSION... 400 PM CDT

THE FIRST ISSUE IS THE FREEZING RAIN TONIGHT. WE HAVE ADVISORY FOR ALL OF THE CWA AT ONE TIME OR ANOTHER. THE COLD FRONT WAS FROM GARY INDIANA TO ST LOUIS AT 19 UTC. AS THE COLD AIR MOVES INTO NORTHEAST ILLINOIS AND NORTHWEST INDIANA...WARM AIR OVERRIDES IT AND THIS CREATES PRECIPITATION. USING A CROSS SECTION OF EQUIVALENT POTENTIAL TEMPERATURE WE SEE THAT THIS COLD AIR IS SHALLOW. UP TO THE 800 MB LEVEL. ACARS SOUNDINGS AT ORD SHOWS THE AIR ABOVE FREEZING UP TO 737 MB. WEST OF A LINE FROM BOONE MCHENRY BORDER TO EASTERN FORD COUNTY THE DRIZZLE AND FREEZING RAIN HAS BEGUN. EAST OF THAT LINE THE TEMPERATURE HAS NOT FALLEN BELOW 0 DEGREES C NEAR THE SURFACE AND UP TO 800 MB YET.

THE FORECAST SOUNDING FROM THE LOCALLY RUN WRF ARW MODEL SHOWS A LAYER OF THE ATMOSPHERE FROM 896 MB TO 716 MB ABOVE FREEZING. ABOVE THAT THE MOISTURE IN THE AIR IS NEARLY IN EQUILIBRIUM WITH THE VAPOR PRESSURE OF WATER. THIS IS AROUND PONTIAC. THERE MAY BE SOME ICE CRYSTAL FORMING AND SO WE WILL ADD ICE PELLETS FOR BENTON COUNTY INDIANA TONIGHT. OTHERWISE WE WILL FORECAST DRIZZLE AND FREEZING RAIN TONIGHT UP TO AROUND 2 AM. AFTER 06 UTC THE ISENTROPIC LIFT ON THE 285K SURFACE DECREASES AND THERE WILL BE COLD AND DRIER AIR INTO THE REGION.

THE SNOW STORM ON SUNDAY THROUGH MONDAY WILL BE THE NEXT WEATHER EVENT. WE USED THE GFS...NAM AND NGM MODELS FOR THIS FORECAST. A CYCLONE IS FORECAST TO DEVELOP IN TEXAS. 850 MB AND 1000 MB TEMPERATURE GRADIENTS AND TEMPERATURE ADVECTION ARE OPERATED ON BY A LAPLACIAN AND INTEGRATED UP TO 850 MB SHOW INCREASE IN LOW LEVEL VORTICITY OVER ARKANSAS BY 00 UTC MONDAY. A LOW WILL DEVELOP THERE AND MOVE INTO KENTUCKY BY 06 UTC MONDAY. THE TRACK OF THE 850 MB TROUGH AND Q VECTORS PUT AN AREA OF LIFT MOVING FROM SOUTHEAST IOWA AND MOVES IT THROUGH CHICAGO BY 12 UTC MONDAY. THIS WILL PROVIDE SOME FORCING FOR SNOW SUNDAY NIGHT AND EARLY MONDAY MORNING. THICKNESS FORECAST SHOW THE SOUTHERN THIRD OF THE FORECAST AREA WILL HAVE SOME MIXED PRECIPITATION FREEZING RAIN AND ICE PELLETS. THERE IS ENOUGH MOISTURE ABOVE -12 DEGREES CELSIUS THAT ICE CRYSTALS WILL FORM AND FALL. THERE MAY BE SUPERCOOLED WATER DROPS AS WELL SUNDAY AND SUNDAY AFTERNOON. BY SUNDAY NIGHT THE WHOLE COLUMNOF AIR MAY BE COLD ENOUGH FOR SNOW. WE WILL FORECAST ALL SNOW SUNDAY NIGHT INTO MONDAY. THIS STORM EVENT WILL END MONDAY AFTERNOON. THE LOW WILL MOVE INTO PENNSYLVANIA. WE EXPECT ABOUT 4 TO 7 INCHES OF SNOW FOR THE WHOLE AREA BY MONDAY AFTERNOON AT THIS TIME.

&&

.AVIATION... 630 PM CST

RE THE 00Z TAFS...CDFNT CONTS TO PUSH SEWRD AND HAS REACHED A GRR-LAF-BLV LN AT SUNSET. COLD AIR LAGGING WSHFT BUT MAKING A LITTLE QUICKER PROGRESS INTO CENTRAL IL. NEXT SHRTWV LIFTING ACROSS IA SPREADING PRECIP SHIELD BACK INTO NRN IL FM NRN MO. APPEARS NRN EXTENT OF PRECIP WILL REACH FAR SRN LK MI AND SRN PORTION OF CHI METRO AREA INCLUDING MDW...BUT FEEL ORD SHUD ESCAPE AND ONLY SEE OCNL -DZ AS CONT LLVL COLD AIR ADVECTION SATURATES BL AND SQUEEZES OUT DZ. SFC TEMPS AOB FREEZING ACROSS NC IL WILL EVENTUALLY SPREAD INTO NE IL CHANGING SPOTTY -DZ TO -FZDZ THIS EVE BEFORE SFC DWPT DEPRESSIONS GROW LARGE ENUF TO END BR AND -DZ. AFTER SHRTWV PASSES BY THIS TONIGHT PRECIP BAND EXPECTED TO BE SUPRESSES A LITTLE FURTHER S INTO CNTRL AND SRN IL INTO CNTRL IND LEAVING TERMINALS DRY FOR REMAINDER OF VALID FCST PD. AS NEXT SHRTWV APPROACHES LATE SAT AFTERNOON AND EARLY SAT EVE WAA AND INSENTROPIC LIFT SPREADS BACK TOWARD NRN IL BUT PRECIP ARIVAL...IN THE FORM OF SN FOR THE TERMINALS...EXC GYY WHICH WILL LIKELY SEE MIXTURE...NOT FORESEEN TIL AFT 00Z SUN.

TRS

&&

.LOT WATCHES/WARNINGS/ADVISORIES... .IL...FREEZING RAIN ADVISORY MCHENRY LAKE COOK DUPAGE KANE KENDALL WILL UNTIL 08Z. FREEZING RAIN ADVISORY LASALLE GRUNDY KANKAKEE LIVINGSTON FORD IROQUIOUS UNTIL 12Z. .IN...FREEZING RAIN ADVISORY LAKE AND PORTER UNTIL 08Z. FREEZING RAIN ADVISORY NEWTON JASPER BENTON UNTIL 12Z. .LM...SMALL CRAFT ADVISORY FOR ALL NEAR SHORE UNTIL 15Z.

&&

$$

.DISCUSSION... 400 PM CDT

THE FIRST ISSUE IS THE FREEZING RAIN TONIGHT. WE HAVE ADVISORY FOR ALL OF THE CWA AT ONE TIME OR ANOTHER. THE COLD FRONT WAS FROM GARY INDIANA TO ST LOUIS AT 19 UTC. AS THE COLD AIR MOVES INTO NORTHEAST ILLINOIS AND NORTHWEST INDIANA...WARM AIR OVERRIDES IT AND THIS CREATES PRECIPITATION. USING A CROSS SECTION OF EQUIVALENT POTENTIAL TEMPERATURE WE SEE THAT THIS COLD AIR IS SHALLOW. UP TO THE 800 MB LEVEL. ACARS SOUNDINGS AT ORD SHOWS THE AIR ABOVE FREEZING UP TO 737 MB. WEST OF A LINE FROM BOONE MCHENRY BORDER TO EASTERN FORD COUNTY THE DRIZZLE AND FREEZING RAIN HAS BEGUN. EAST OF THAT LINE THE TEMPERATURE HAS NOT FALLEN BELOW 0 DEGREES C NEAR THE SURFACE AND UP TO 800 MB YET.

THE FORECAST SOUNDING FROM THE LOCALLY RUN WRF ARW MODEL SHOWS A LAYER OF THE ATMOSPHERE FROM 896 MB TO 716 MB ABOVE FREEZING. ABOVE THAT THE MOISTURE IN THE AIR IS NEARLY IN EQUILIBRIUM WITH THE VAPOR PRESSURE OF WATER. THIS IS AROUND PONTIAC. THERE MAY BE SOME ICE CRYSTAL FORMING AND SO WE WILL ADD ICE PELLETS FOR BENTON COUNTY INDIANA TONIGHT. OTHERWISE WE WILL FORECAST DRIZZLE AND FREEZING RAIN TONIGHT UP TO AROUND 2 AM. AFTER 06 UTC THE ISENTROPIC LIFT ON THE 285K SURFACE DECREASES AND THERE WILL BE COLD AND DRIER AIR INTO THE REGION.

THE SNOW STORM ON SUNDAY THROUGH MONDAY WILL BE THE NEXT WEATHER EVENT. WE USED THE GFS...NAM AND NGM MODELS FOR THIS FORECAST. A CYCLONE IS FORECAST TO DEVELOP IN TEXAS. 850 MB AND 1000 MB TEMPERATURE GRADIENTS AND TEMPERATURE ADVECTION ARE OPERATED ON BY A LAPLACIAN AND INTEGRATED UP TO 850 MB SHOW INCREASE IN LOW LEVEL VORTICITY OVER ARKANSAS BY 00 UTC MONDAY. A LOW WILL DEVELOP THERE AND MOVE INTO KENTUCKY BY 06 UTC MONDAY. THE TRACK OF THE 850 MB TROUGH AND Q VECTORS PUT AN AREA OF LIFT MOVING FROM SOUTHEAST IOWA AND MOVES IT THROUGH CHICAGO BY 12 UTC MONDAY. THIS WILL PROVIDE SOME FORCING FOR SNOW SUNDAY NIGHT AND EARLY MONDAY MORNING. THICKNESS FORECAST SHOW THE SOUTHERN THIRD OF THE FORECAST AREA WILL HAVE SOME MIXED PRECIPITATION FREEZING RAIN AND ICE PELLETS. THERE IS ENOUGH MOISTURE ABOVE -12 DEGREES CELSIUS THAT ICE CRYSTALS WILL FORM AND FALL. THERE MAY BE SUPERCOOLED WATER DROPS AS WELL SUNDAY AND SUNDAY AFTERNOON. BY SUNDAY NIGHT THE WHOLE COLUMNOF AIR MAY BE COLD ENOUGH FOR SNOW. WE WILL FORECAST ALL SNOW SUNDAY NIGHT INTO MONDAY. THIS STORM EVENT WILL END MONDAY AFTERNOON. THE LOW WILL MOVE INTO PENNSYLVANIA. WE EXPECT ABOUT 4 TO 7 INCHES OF SNOW FOR THE WHOLE AREA BY MONDAY AFTERNOON AT THIS TIME.

&&

.AVIATION... 630 PM CST

RE THE 00Z TAFS...CDFNT CONTS TO PUSH SEWRD AND HAS REACHED A GRR-LAF-BLV LN AT SUNSET. COLD AIR LAGGING WSHFT BUT MAKING A LITTLE QUICKER PROGRESS INTO CENTRAL IL. NEXT SHRTWV LIFTING ACROSS IA SPREADING PRECIP SHIELD BACK INTO NRN IL FM NRN MO. APPEARS NRN EXTENT OF PRECIP WILL REACH FAR SRN LK MI AND SRN PORTION OF CHI METRO AREA INCLUDING MDW...BUT FEEL ORD SHUD ESCAPE AND ONLY SEE OCNL -DZ AS CONT LLVL COLD AIR ADVECTION SATURATES BL AND SQUEEZES OUT DZ. SFC TEMPS AOB FREEZING ACROSS NC IL WILL EVENTUALLY SPREAD INTO NE IL CHANGING SPOTTY -DZ TO -FZDZ THIS EVE BEFORE SFC DWPT DEPRESSIONS GROW LARGE ENUF TO END BR AND -DZ. AFTER SHRTWV PASSES BY THIS TONIGHT PRECIP BAND EXPECTED TO BE SUPRESSES A LITTLE FURTHER S INTO CNTRL AND SRN IL INTO CNTRL IND LEAVING TERMINALS DRY FOR REMAINDER OF VALID FCST PD. AS NEXT SHRTWV APPROACHES LATE SAT AFTERNOON AND EARLY SAT EVE WAA AND INSENTROPIC LIFT SPREADS BACK TOWARD NRN IL BUT PRECIP ARIVAL...IN THE FORM OF SN FOR THE TERMINALS...EXC GYY WHICH WILL LIKELY SEE MIXTURE...NOT FORESEEN TIL AFT 00Z SUN.

TRS

&&

.LOT WATCHES/WARNINGS/ADVISORIES... .IL...FREEZING RAIN ADVISORY THROUGH 8 PM FOR NORTH CENTRAL IL. FREEZING RAIN ADVISORY THROUGH 2 AM FOR NORTHEAST IL. .IN...FREEZING RAIN ADVISORY THROUGH 2 AM FOR NORTHWEST IN. .LM...SMALL CRAFT ADVISORY FOR ALL NEAR SHORE UNTIL MID SAT AM. &&

$$

.DISCUSSION...

THE FIRST ISSUE IS THE FREEZING RAIN TONIGHT. WE HAVE ADVISORY FOR ALL OF THE CWA AT ONE TIME OR ANOTHER. THE COLD FRONT WAS FROM GARY INDIANA TO ST LOUIS AT 19 UTC. AS THE COLD AIR MOVES INTO NORTHEAST ILLINOIS AND NORTHWEST INDIANA...WARM AIR OVERRIDES IT AND THIS CREATES PRECIPITATION. USING A CROSS SECTION OF EQUIVALENT POTENTIAL TEMPERATURE WE SEE THAT THIS COLD AIR IS SHALLOW. UP TO THE 800 MB LEVEL. ACARS SOUNDINGS AT ORD SHOWS THE AIR ABOVE FREEZING UP TO 737 MB. WEST OF A LINE FROM BOONE MCHENRY BORDER TO EASTERN FORD COUNTY THE DRIZZLE AND FREEZING RAIN HAS BEGUN. EAST OF THAT LINE THE TEMPERATURE HAS NOT FALLEN BELOW 0 DEGREES C NEAR THE SURFACE AND UP TO 800 MB YET.

THE FORECAST SOUNDING FROM THE LOCALLY RUN WRF ARW MODEL SHOWS A LAYER OF THE ATMOSPHERE FROM 896 MB TO 716 MB ABOVE FREEZING. ABOVE THAT THE MOISTURE IN THE AIR IS NEARLY IN EQUILIBRIUM WITH THE VAPOR PRESSURE OF WATER. THIS IS AROUND PONTIAC. THERE MAY BE SOME ICE CRYSTAL FORMING AND SO WE WILL ADD ICE PELLETS FOR BENTON COUNTY INDIANA TONIGHT. OTHERWISE WE WILL FORECAST DRIZZLE AND FREEZING RAIN TONIGHT UP TO AROUND 2 AM. AFTER 06 UTC THE ISENTROPIC LIFT ON THE 285K SURFACE DECREASES AND THERE WILL BE COLD AND DRIER AIR INTO THE REGION.

THE SNOW STORM ON SUNDAY THROUGH MONDAY WILL BE THE NEXT WEATHER EVENT. WE USED THE GFS...NAM AND NGM MODELS FOR THIS FORECAST. A CYCLONE IS FORECAST TO DEVELOP IN TEXAS. 850 MB AND 1000 MB TEMPERATURE GRADIENTS AND TEMPERATURE ADVECTION ARE OPERATED ON BY A LAPLACIAN AND INTEGRATED UP TO 850 MB SHOW INCREASE IN LOW LEVEL VORTICITY OVER ARKANSAS BY 00 UTC MONDAY. A LOW WILL DEVELOP THERE AND MOVE INTO KENTUCKY BY 06 UTC MONDAY. THE TRACK OF THE 850 MB TROUGH AND Q VECTORS PUT AN AREA OF LIFT MOVING FROM SOUTHEAST IOWA AND MOVES IT THROUGH CHICAGO BY 12 UTC MONDAY. THIS WILL PROVIDE SOME FORCING FOR SNOW SUNDAY NIGHT AND EARLY MONDAY MORNING. THICKNESS FORECAST SHOW THE SOUTHERN THIRD OF THE FORECAST AREA WILL HAVE SOME MIXED PRECIPITATION FREEZING RAIN AND ICE PELLETS. THERE IS ENOUGH MOISTURE ABOVE -12 DEGREES CELSIUS THAT ICE CRYSTALS WILL FORM AND FALL. THERE MAY BE SUPERCOOLED WATER DROPS AS WELL SUNDAY AND SUNDAY AFTERNOON. BY SUNDAY NIGHT THE WHOLE COLUMNOF AIR MAY BE COLD ENOUGH FOR SNOW. WE WILL FORECAST ALL SNOW SUNDAY NIGHT INTO MONDAY. THIS STORM EVENT WILL END MONDAY AFTERNOON. THE LOW WILL MOVE INTO PENNSYLVANIA. WE EXPECT ABOUT 4 TO 7 INCHES OF SNOW FOR THE WHOLE AREA BY MONDAY AFTERNOON AT THIS TIME.

&&

.AVIATION... 1200 PM CST

FOR THE 18Z TAFS...FRONTAL BOUNDARY SLOWLY MOVING SOUTH FROM CURRENT POSITION INVOF A ORD-PNT LINE. AS COLDER AIR ASSOCIATED WITH THIS BOUNDARY ENCOUNTERS THE VERY MOIST AIR OUT AHEAD OF THE FRONT...LIFR CIGS ARE RESULTING. SCT -SN/RA OVR SERN IA IS TRACKING NEWD AT 60KTS IN CONJUNCTION WITH A WEAK MID-LEVEL DISTURBANCE. AT CURRENT PACE...THIS PRECIP SHOULD REACH RFD AROUND 19Z AND ORD/MDW/DPA AROUND 20Z. LOW LEVEL TEMPS STILL ABV FREEZING BUT WILL BE DIPPING BELOW THAT BY EVENING IN THE RFD AREA. VERTICAL TEMP PROFILES COOL BELOW 0 DEG C AT THE CHICAGO AREA TERMINALS LATE THIS EVENING. SATURATED SUB-FREEZING LAYER BTWN THE SFC AND ~5KFT SHOULD ONLY BE ABOUT -5 TO -8C AT ITS COLDEST POINT. THUS...SNOWFLAKE GENERATION OVERNIGHT MAY BE HARD PRESSED TO HAPPEN...LEAVING SUPERCOOLED LIQUID (FZDZ) THE MOST LIKELY SCENARIO. HEAVIER PRECIP SHOULD REMAIN WELL SOUTH OF THE LOCAL TERMINALS THROUGH THE NEXT 24HRS. CIGS SHOULD CLIMB BACK INTO MVFR RANGE BY MORNING AS 1035-MB HIGH TO THE NW NUDGES DRIER AIR DEEPER INTO OUR AREA.

HANDEL

&&

.LOT WATCHES/WARNINGS/ADVISORIES... .IL...FREEZING RAIN ADVISORY THROUGH 8 PM FOR NORTH CENTRAL IL. FREEZING RAIN ADVISORY THROUGH 2 AM FOR NORTHEAST IL. .IN...FREEZING RAIN ADVISORY THROUGH 2 AM FOR NORTHWEST IN. .LM...SMALL CRAFT ADVISORY FOR ALL NEAR SHORE UNTIL MID SAT AM. &&

$$

.DISCUSSION FOR MORNING GRIDS/ZONES... 330 AM CST

MAIN FORECAST CONCERNS CONTINUE TO CENTER ON EVOLUTION OF COMPLEX UPPER LEVEL PATTERN EVOLVING ACROSS THE WESTERN CONUS...AND THE POTENTIAL WINTER STORM FOR THE LATTER PART OF THE WEEKEND.

IN THE NEAR TERM...STRONG SOUTHERLY SURFACE GRADIENT HAS ALLOWED FOR WINDS STAYING UP INTO THE 25 TO 30 MPH RANGE OVERNIGHT...AND EXPECTING WINDY CONDITIONS TO PERSIST INTO TODAY WITH MAIN COLD FRONTAL BOUNDARY EXTENDING FROM CENTRAL MINNESOTA THROUGH CENTRAL KANSAS. SHOULD SEE INCREASE IN CLOUDINESS TODAY AS INITIALLY HIGH CLOUD COVER INCREASES...WITH LOWER CLOUDS BECOMING PREVALENT LATER THIS AFTERNOON WITH BETTER LOW LEVEL MOISTURE IN ADVANCE OF THE APPROACHING FRONT. ALSO...A SERIES OF WEAK VORTS WILL EJECT INTO THE MID MISSISSIPPI RVR VALLEY THIS AFTERNOON AND TONIGHT WITH AN UPPER SPEED MAX NOSING INTO WEST CENTRAL ILLINOIS THIS EVENING. LOW LEVEL MOISTURE WILL DEEPEN INTO THIS EVENING...BUT UPSTREAM RAOBS SHOWING A VERY DRY MID LEVEL AIR MASS ACROSS THE CENTRAL/SOUTHERN PLAINS FROM 00Z LAST EVENING...AND RATHER LARGE MID LEVEL DEW PT DEPRESSIONS DO PERSIST IN FORECAST SOUNDINGS ACROSS THE FORECAST AREA THIS EVENING. MAINTAINED THE LIKELY POPS FOR -RA GIVEN THE ABOVE FACTORS BUT THIS DOES APPEAR AS THOUGH IT WILL BE A HIGH COVERAGE/LOW QPF TYPE SITUATION WITH RATHER INEFFICIENT PRECIP PRODUCTION GIVEN DRIER MID LEVELS. MAY EVEN TURN OUT TO BE MORE OF A DRIZZLY TYPE EVENT FOR SOME AREAS BUT FOR NOW WILL JUST MAINTAIN LIKELY POPS FOR -RA/DZ.

A MORE PROGRESSIVE NORTHERN STREAM TROUGH WILL SKIRT ACROSS THE US/CANADIAN BORDER THROUGH FRIDAY AFTERNOON WHILE THE UPPER LEVEL LOW WITH THE SOUTHERN STREAM DROPS INTO THE SOUTHWEST CONUS. THE MORE PROGRESSIVE NORTHERN STREAM WILL ALLOW THE COLD FRONTAL BOUNDARY TO TRACK INTO NORTHERN ILLINOIS BY FRIDAY MORNING. BEST CHANCE OF PRECIP ON FRIDAY SHOULD BE ACROSS MAINLY SERN HALF OF THE CWA WITH THE APPROACHING LOW LEVEL FRONT AND A FAVORABLE PROXIMITY TO THE ENTRANCE REGION OF THE UPPER STREAK MOVING ACROSS THE AREA. MAY SEE SLOWLY FALLING TEMPS ACROSS THE NORTH WITH THE COLD AIR ADVECTION AND FORECAST SOUNDINGS BECOME MORE MARGINAL IN TERMS OF PRECIP TYPE BY LATE AFTERNOON. MAY SEE SOME SLEET/SNOW MIX IN ACROSS THE NORTH IN THE AFTERNOON BUT PRECIP IS NOT EXPECTED TO BE AS WIDESPREAD ACROSS THE NORTH SO NOT EXPECTING THIS FIRST ROUND OF PRECIP TO POSE ANY SIGNIFICANT PROBLEMS. LOW LEVEL FRONT SHOULD SAG FAR ENOUGH SOUTH TO REALLY DWINDLE PRECIP CHANCES FRIDAY NIGHT INTO SATURDAY AFTERNOON.

STILL QUITE A FEW UNCERTAINTIES EXIST REGARDING EVOLUTION OF SOUTHWEST CONUS UPPER TROUGH SAT/MON. THE GFS REMAINS A LITTLE MORE PROGRESSIVE EJECTING THIS UPPER TROUGH INTO THE PLAINS IN COMPARISON TO LATTER PERIODS OF THE WRF AND THE CANADIAN. THE GFS DOES HAVE SOME SUPPORT FROM THE 21Z NCEP ENSEMBLE MEANS...ALTHOUGH INDIVIDUAL ENSEMBLE MEMBERS SHOW SOME RATHER LARGE DIFFERENCES. THE 00Z ECMWF ALSO SEEMS MORE SUPPORTIVE OF A GFS TYPE SOLUTION. HPC HAS PREFERRED A SOLUTION CLOSER TO THE 21Z SREF ENSEMBLE MEANS WHICH IS MORE PROGRESSIVE THAN THE NAM. GIVEN THESE ABOVE FACTORS HAVE PUT A LITTLE MORE WEIGHT ON THE GFS FOR THE WEEKEND. INCREASED POPS AGAIN LATE SATURDAY NIGHT INTO SUNDAY AS LOW LEVEL WARM FRONT SHARPENS TO THE SOUTH WITH STRENGTHENING ISENTROPIC LIFT INTO SUNDAY MORNING. BEST CHANCE OF SIGNIFICANT MIXED PRECIP APPEARS TO BE ON SUNDAY ACROSS MAINLY SOUTHERN HALF OF THE CWA WHERE WARM LAYER COULD SUPPORT MIX OF FZRA/SLEET/SNOW. FURTHER TO NORTH...WILL MAINTAIN LIKELY POPS FOR SNOW DURING THE AFTERNOON. IT STILL APPEARS BEST CHANCE FOR SIGNIFICANT SNOW WILL OCCUR SUNDAY NIGHT INTO EARLY MONDAY AS MAIN MID/UPPER LEVEL WAVE MOVES INTO THE SOUTHERN GREAT LAKES. DID KEEP MENTION OF FZRA/SLEET MAINLY FOR NWRN INDIANA COUNTIES INTO SUNDAY EVENING. GREATEST SNOW ACCUMS AT THIS POINT STILL APPEAR TO BE NORTH OF I-80 DURING THIS PERIOD BUT STILL SOME QUESTIONS REMAIN GIVEN UNCERTAINTY WITH THE UPPER LEVEL EVOLUTION DURING THIS PERIOD.

MARSILI &&

.AVIATION... 1040 PM CST

RE 06Z TAFORS...TIGHT PRESSURE GRADIENT BETWEEN STRONG HI PRES RIDGE OVER THE STRETCHED ALONG THE APPALACHIANS AND SFC LO CROSSING FROM THE ERN DAKOTAS INTO W CENTRAL MN. SSW-SW LLJ 50-60KTS WITHIN 1KM OF SFC PER ACARS CHI VC SO EVEN WITH ONLY A FRACTION OF MOMENTUM DONW TO SFC STILL WILL GET GUSTS TO AROUND 25KTS THRU THE NITE. GRADIENT SLOWLY RELAXES DURG THU AS THE SFC LOW TREKS ACROSS LK SUP AND THE CDFNT PUSHES INTO WI AND IA BY 00Z FRI. ONLY A FEW PATCHES OF CI DURING THE OVERNIGHT THEN EXPECT STRATOCU TO QUICKLY ADVECT ARCROSS THE MID MS VALLEY MIDDAY THU GULF MOISTURE NOW STARTING TO STREAM NWRD FM THE WRN GULF INTO ERN TX ABD SRN OK. WITH MOISTURE ARRIVING DURG LATER THU AND INITIAL SHORT WAVE TROF MOVING QUICKLY FM THE CENTRAL PLAINS ACROSS THE MS VALLEY LATE THRU AFTERNOON ANF TO LK MI BY 06Z HAVE INCLUDED A PROB30 FOR -SHRA DURG THU EVE.

TRS &&

.LOT WATCHES/WARNINGS/ADVISORIES... .IL...NONE. .IN...NONE. .LM...GALE WARNING IN EFFECT FOR OPEN WATERS THROUGH THIS AFTERNOON. SMALL CRAFT ADV ALL NEARSHORE WATERS THROUGH THIS EVENING.

&&

$$

.DISCUSSION FOR AFTERNOON GRIDS/ZONES... 240 PM CST SYNOPSIS...COMPLEX EVOLUTION OF GENERAL UPPER TROUGH OVER INTERIOR NORTH AMERICA HAS BEGUN. TREND TOWARD COLDER TEMPS AND INCREASING RAIN..SNOW AND MIXED PRECIP WILL OCCUR DURING THIS TRANSITION WITH POTENTIALLY SIGNIFICANT SNOW SUNDAY NIGHT AND MONDAY.

DISCUSSION...APPROACHING SURFACE LOW OVER THE WESTERN DAKOTAS THIS AFTERNOON SPREADING HEIGHT FALLS AND INCREASING S-SE WINDS INTO THE WESTERN LAKES. WHILE TEMPS TODAY HAVE BEEN LAGGING DUE TO CLOUD COVER EXPECT MINS TONIGHT TO BE RATHER FLAT AND LKLY RISE IN THE NIGHT AS S WINDS INCREASE.

UPPER TROUGH SAGGING INTO PLATO STATES TNGT AND THURS WHILE APPROACHING LOW RACES BY TO THE NORTH. THUS A HIGH AMPLITUDE POSTIVE TILTED TROUGH IS SETTING UP WHICH WILL FOCUS AN ACTIVE BAROCLINC ZONE THROUGH THE MIDWEST OVER THE WEEKEND. COLD FRONT IN WAKE OF APPROACHING LOW WILL LIE OUT FROM CENTRAL PLAINS INTO NRN GT LAKES LATE THURS WITH RETURNING WARM ADVECTION MSTR STREAMING NEWD. ISENTROPIC LIFT AND SOME JET DYNAMICS SHOULD KICK OFF RAIN THROUGH MISS VLY INTO SRN LAKES THURS AFTERNOON CONTINUING AT NIGHT. EXPECT COLD AIR TO SAG INTO REGION FROM NORTH DURING THE DAY FRIDAY WITH POSSIBLE WEAK WAVES MOVING UP THE FRONTAL ZONE FRIDAY NIGHT.

MODEL SOUNDINGS SUGGEST RAIN WILL MIX WITH SLEET OR FREEZING RAIN FRI NIGHT OR EARLY SATURDAY ESPECIALLY TOWARDS WISC BORDER. EXPECT ARCTIC FRONT TO CONTINUE SAGGING SWD POSSIBLY REACHING OHIO VLY BY SATURDAY NIGHT. THIS WILL DECREASE PRECIP WHICH BY THEN WOULD BE SNOW. LITTLE IF ANY SNOW ACCUMLTN EXPECTED FROM THIS FIRST ROUND.

MAIN UPPER TROUGH FORECAST TO EJECT FROM SW STATES SUNDAY INTO MONDAY KICKING OFF SFC LOW OVER LOWER MISS VLY WHICH TRACKS NEWD INTO INDIANA MONDAY MORNING. WHILE GFS HAS BEEN CONSISTENT WITH THIS SCENARIO...THE TRACK AND INTENSITY HAVE BEEN VARIABLE. ALSO...TIMING OF SYSTEMS COMING OUT OF THE SW ARE PRONE TO BEING TOO FAST IN THE WORLD OF SIMULATION. NONETHELESS..THE OVERALL PICTURE CONTINUES TO FAVOR A POTENTIAL FOR A SIGNIFICANT SNOW SITUATION FOR NORTHERN ILL AND NW INDIANA SUNDAY NIGHT INTO MONDAY. DEPTH OF COLD AIR SHOULD BE SUFFICIENT TO PRECLUDE MIXED PRECIP OVER NW 2/3 OF FCST AREA. HOWEVER..MANY QUESTIONS REMAIN AND LATER GUIDANCE SHOULD HELP SORT THIS OUT. MOST DETAILS OF MID AND LONG TERM FCST HAVE NOT BEEN CHANGED DUE TO HIGH DEGREE OF UNDERTAINTY.

WITH BROAD TROUGH SETTING UP OVER INTERIOR NA...BELOW AVE TEMPS EXPECTED FROM TUE ONWARD. FCST MINS COULD BE TOO WARM TUE AND WED MORNINGS IF SNOW COVER MATERIALIZES. KML &&

.AVIATION... 1040 PM CST

RE 06Z TAFORS...TIGHT PRESSURE GRADIENT BETWEEN STRONG HI PRES RIDGE OVER THE STRETCHED ALONG THE APPALACHIANS AND SFC LO CROSSING FROM THE ERN DAKOTAS INTO W CENTRAL MN. SSW-SW LLJ 50-60KTS WITHIN 1KM OF SFC PER ACARS CHI VC SO EVEN WITH ONLY A FRACTION OF MOMENTUM DONW TO SFC STILL WILL GET GUSTS TO AROUND 25KTS THRU THE NITE. GRADIENT SLOWLY RELAXES DURG THU AS THE SFC LOW TREKS ACROSS LK SUP AND THE CDFNT PUSHES INTO WI AND IA BY 00Z FRI. ONLY A FEW PATCHES OF CI DURING THE OVERNIGHT THEN EXPECT STRATOCU TO QUICKLY ADVECT ARCROSS THE MID MS VALLEY MIDDAY THU GULF MOISTURE NOW STARTING TO STREAM NWRD FM THE WRN GULF INTO ERN TX ABD SRN OK. WITH MOISTURE ARRIVING DURG LATER THU AND INITIAL SHORT WAVE TROF MOVING QUICKLY FM THE CENTRAL PLAINS ACROSS THE MS VALLEY LATE THRU AFTERNOON ANF TO LK MI BY 06Z HAVE INCLUDED A PROB30 FOR -SHRA DURG THU EVE.

TRS &&

.LOT WATCHES/WARNINGS/ADVISORIES... .IL...NONE. .IN...NONE. .LM...GALE WARNING IN EFFECT THROUGH THURSDAY AFTERNOON FOR THE OPEN WATERS. SMALL CRAFT ADVISORY IN EFFECT UNTIL 06Z FRIDAY.

&&

$$

.SHORT TERM (TODAY AND TONIGHT)...

WE DO NOT EXPECT TEMPERATURES TO DROP MUCH THIS MORNING FROM THE 25 TO 30 DEGREE RANGE REPORTED AT 07Z. EARLY MORNING ACARS SOUNDINGS FROM SDF INDICATED A 35KT LOW LEVEL SOUTHERLY FLOW WHICH WILL ONLY INTENSIFY DURING THIS FORECAST PERIOD WITH 8H WINDS EXPECTED TO INCREASE TO 50KTS BY 06Z FRIDAY. ALONG WITH THE INCREASING WIND FIELDS WILL COME INCREASING MOISTURE. THE 305K ISENTROPIC CHART INDICATES 90RH OVER THE FORECAST AREA BY 12Z FRIDAY. WILL MENTION LOW CHANCE POPS OVER THE NORTHWEST PORTION OF THE CWFA SHORTLY AFTER 00Z FRIDAY AND INCREASE POPS INTO THE LIKELY CATEGORY ACROSS ALL OF THE AREA BY 12Z FRIDAY.

WE EXPECT SUNNY SKIES THIS MORNING BUT WILL BEGIN TO SEE INCREASING HIGH CLOUDS DURING THE AFTERNOON. TEMPERATURES WILL WARM INTO THE MID AND UPPER 50S THIS AFTERNOON AND WITH THE SOUTHERLY FLOW LOWS TONIGHT WILL NOT FALL MUCH. --JA

LONG TERM (FRIDAY THROUGH WEDNESDAY)

...WILL ISSUE A FLOOD WATCH STARTING FRIDAY EVENING AND CONTINUING THROUGH SUNDAY...

MAIN CONCERNS IN THE EXTENDED WILL CENTER AROUND RAINFALL AMOUNTS AND POSSIBLE FLOODING THIS WEEKEND.

.FRIDAY THROUGH SUNDAY...

UPPER AIR PATTERN FRIDAY WILL FEATURE A STRONG POSITIVELY TILTED TROUGH ACROSS THE INTERMOUNTAIN WEST...A SUBTROPICAL RIDGE CENTERED EAST OF FLORIDA...AND A STRONG SOUTHWESTERLY JET EXTENDING FROM THE SOUTHERN ROCKIES TO THE GREAT LAKES AREA. ALTHOUGH THE UPPER PATTERN WILL NOT CHANGE MUCH... A SHALLOW ARCTIC FRONT WILL SAG SOUTHEAST ACROSS THE LOWER MISSOURI VALLEY. THE OPERATIONAL GFS IS FASTER AND FARTHER SOUTH WITH THIS FRONT...FORECASTING IT TO MOVE SOUTH OF THE OHIO RIVER EARLY SATURDAY...WHILE THE NAM HOLD IT FARTHER NORTHWEST ACROSS CENTRAL INDIANA.

MOISTURE TRANSPORT NORTHWARD ON THE WESTERN EDGE OF THE SUBTROPICAL RIDGE WILL BE NOTABLE...WITH PRECIPITABLE WATER TOTALS EXCEEDING ONE INCH...OR THREE STANDARD DEVIATIONS ABOVE NORMAL...EXTENDING NORTHEASTWARD ALONG THE OHIO RIVER VALLEY FRIDAY THROUGH SUNDAY.

WITH THIS TYPE OF UPPER AIR PATTERN...THE TIMING OF INDIVIDUAL DISTURBANCES MOVING NORTHEAST ALONG THE JET WILL BE DIFFICULT TO TIME...AND THROUGH SATURDAY AT LEAST...DO NOT EXPECT ANY SURFACE LOW PRESSURE TO DEVELOP ACROSS THE OHIO VALLEY...ONLY A WEAK TROUGH WILL REFLECT THE LOCATION OF THE SURFACE BOUNDARY. HOWEVER...THE COMBINATION OF LIFT ASSOCIATED WITH THE UPPER JET...SURFACE CONVERGENCE...AND HIGH PW VALUES...WILL BRING OCCASIONAL MODERATE RAINS BEGINNING LATE FRIDAY AND EXTENDING THROUGH SATURDAY. FORECAST PRECIPITATION AMOUNTS AND LOCATION OF THE AXIS OF HEAVIEST RAIN DIFFER BETWEEN THE DRIER NAM...AND THE GFS...BUT WIDESPREAD RAINFALL AMOUNTS OF 2 TO 3 INCHES...WITH LOCALLY HIGHER AMOUNTS...ARE POSSIBLE FOR THE THREE DAY WEEKEND PERIOD ACROSS THE CWA.

EXPECT QUITE MILD TEMPERATURES FRIDAY INTO EARLY SATURDAY AS STRONG SOUTHERLY WINDS WILL BE IN PLACE. TEMPERATURES SATURDAY AND SUNDAY WILL BE TRICKY AND WILL DEPEND ON EXACT LOCATION OF SURFACE BOUNDARY. VARIOUS MODEL SOLUTIONS HAVE HIGHS SATURDAY ALONG THE OHIO RIVER RANGING FROM THE MID 40S TO THE UPPER 50S. WILL COMPROMISE WITH A FORECAST SOMEWHERE IN BETWEEN.

ON SUNDAY...RAIN WILL CONTINUE AS WESTERN TROUGH EJECTS INTO THE PLAINS STATES. LOW PRESSURE WILL DEVELOP EARLY SUNDAY ACROSS THE SOUTHERN PLAINS AND MOVE NORTHEAST ALONG THE ARCTIC BOUNDARY THROUGH KENTUCKY LATE IN THE DAY. FORECAST ELEVATED LI`S APPROACH 0 LATE SATURDAY AND SUNDAY. WILL LEAVE IN CHANCE OF THUNDER.

MONDAY THROUGH WEDNESDAY...

A MUCH COLDER PERIOD EXPECTED. WINDS WILL SWITCH TO THE NORTHWEST AS RAIN ENDS EARLY MONDAY AS A DEEPENING SURFACE LOW RAPIDLY MOVES OFF TO THE NORTHEAST. A STRONG COLD HIGH BUILDS INTO THE SOUTHERN PLAINS...DRIVING THE COLD FRONT TOWARDS THE GULF STATES. WITH RESIDUAL MOISTURE REMAINING MONDAY AND TUESDAY...COMBINED WITH MUCH COLDER AIR...WILL MAINTAIN MENTION OF POSSIBLE LIGHT SNOW SHOWERS OR FLURRIES BOTH DAYS. JSD

.LMK WATCHES/WARNINGS/ADVISORIES...

KY...FLOOD WATCH FROM FRIDAY EVENING THROUGH SUNDAY. IN...FLOOD WATCH FROM FRIDAY EVENING THROUGH SUNDAY. &&

$$

.SHORT TERM (TODAY AND TONIGHT)... WATER VAPOR LOOP SHOWS A RIDGE ACROSS THE CENTRAL CONUS...WITH AN UPPER LOW SINKING SOUTH INTO THE PACIFIC NORTHWEST. ACARS 400-250MB WIND OBSERVATIONS REVEAL A NORTHWESTERLY 100KT JET LIFTING INTO NEW ENGLAND. 04Z SURFACE ANALYSIS PLACED A 1034MB ANTICYCLONE ACROSS THE MID ATLANTIC. A WARM/STATIONARY BOUNDARY EXTENDED EAST FROM A 1001MB CYCLONE IN WEST CENTRAL MINNESOTA ALONG THE CANADIAN BORDER AND THE NEW ENGLAND WATERS. A SECOND STATIONARY BOUNDARY CURVED FROM THE LAKE WINNIPEG REGION NORTHEAST THROUGH THE HUDSON BAY.

A CLEAR AND CALM START WITH HIGH PRESSURE DOMINATING SURFACE AND ALOFT. FALLING HEIGHTS ACROSS THE WESTERN CONUS DURING THE SHORT TERM WILL PROMOTE RISING HEIGHTS TO THE EAST. THIS WILL ENCOURAGE SURFACE HIGH PRESSURE TO MOVE OFF THE EAST COAST...AND INITIATE WARM ADVECTION ACROSS THE REGION. FOR TODAY...WENT BELOW MOS HIGH TEMPERATURES BASED ON RECENT PERFORMANCE AND THE LATE AFTERNOON ONSET OF WARM ADVECTION. LIGHT AND VARIABLE WINDS WILL BECOME SOUTHERLY AS THE HIGH MOVES OFF THE EAST COAST THIS AFTERNOON.

HIGH LEVEL MOISTURE WILL TRACK ACROSS THE FORECAST AREA THIS EVENING AND TONIGHT...BUILDING INTO THE MID LEVELS BY MORNING AS WARM ADVECTION INCREASES. COMBINATION OF WARM ADVECTION...LIGHT SOUTHERLY FLOW AND INCREASING CLOUD COVER SHOULD PROVIDE WARMER LOW TEMPERATURES TOMORROW MORNING (GENERALLY 30 TO 35F).

&&

.AVIATION... NO VISIBILITY OR CEILING RESTRICTIONS THROUGH THE TAF CYCLE. SOUTHERLY FLOW INCREASES AS THE SURFACE HIGH MOVES OFF THE EAST COAST THIS AFTERNOON AND TONIGHT. UPPER LEVEL MOISTURE WILL BE OVERSPREADING THIS EVENING...AND LOWERING INTO THE MID LEVELS BY FRIDAY MORNING.

&&

.MARINE... 00Z GFS/ETA MOS AT THOMAS POINT BOTH SUGGEST SUSTAINED WINDS WILL INCREASE FROM 5KTS THIS MORNING TO AROUND 10 KTS THIS AFTERNOON...AND 10-15 KNOTS TONIGHT. 00Z NAM/GFS PROXIMITY LAND BUFKIT FORECAST SOUNDINGS SUGGEST ADDITIONAL WIND GUST MOMENTUM OF UP TO 20 KNOTS POSSIBLE FOR A BRIEF TIME THIS EVENING. WILL GO WITH 15KT WINDS TONIGHT...AND LET LATER SHIFTS MONITOR FOR THE NEED OF A LOW END SMALL CRAFT ADVISORY.

WHILE NOT IDEAL FOR SCA WINDS THIS TIME OF YR...STRONG SW FLOW FRI MORNING THROUGH SAT MORNING IN ADVANCE OF BACKDOOR FRONT COULD BE CONDUCIVE TO SCA EVENT. ATTM WILL HOLD WINDS AT 15 KT SINCE CONFIDENCE IS NOT GREAT AT MIXING DOWN ENOUGH OF THE ENERGY TO BRING WINDS TO SCA LEVEL ON THE WATERS. HWVR BY SUN NGT AND ESPECIALLY ON MONDAY...AGAIN STRONG SW WINDS HWVR GIVEN TIGHTENING GRAD WOULD EXPECT SCA TO BE NECESSARY SOMETIME ON MONDAY OR MONDAY EVNG. FOR NOW WILL JUST MENTION THE POSSIBILITY TO CSTL WATERS DUE TO SOME TIMING ISSUES W/ THE COLD FRONT.

&&

.TIDES... WATER LEVELS ARE CURRENTLY THREE QUARTERS OF A FOOT BELOW ASTRONOMIC PREDICTIONS. THE LUNAR CYCLE IS WANING TOWARD A QUARTER MOON (53% FULL). THE CHESAPEAKE BAY OPERATIONAL FORECAST SYSTEM AND NOAA EXTRATROPICAL STORM SURGE MODEL FORECAST WATER LEVELS TO RECOVER TO NEAR ASTRONOMIC WATER LEVELS THIS AFTERNOON.

&&

.LONG TERM...FRIDAY THROUGH WEDNESDAY...

CLOUDS WILL QUICKLY THICKEN UP FRIDAY MORNING AS MID LEVEL MOISTURE ADVECTS ACROSS THE APPALACHIANS INTO THE MID ATLANTIC. LOW LEVEL FLOW WILL BACK TO SW AND SHOULD ALLOW ADDITIONAL LOW LEVEL MOISTURE TO ADVECT IN DURING THE AFTERNOON. CONVERGENT LOW LEVEL WINDS WILL HELP FORCE PRECIPITATION ACROSS THE REGION BY FRI AFTN...WITH THE BACKDOOR COLD FRONT EXPECTED TO SAG SOUTH FRIDAY NIGHT INTO OUR AREA. HAVE INCREASED POPS A BIT ON FRI WITH LIKELY POPS IN THE NW COUNTIES...TAPERING TO CHC AND LOWER POPS TO THE SE.

BY SAT NGT THE FRONT WILL PROBABLY DROP SOUTH OF THE CWFA AND LOW LEVEL WINDS WILL BECOME ONSHORE FROM THE ATLC DEVELOPING A WEDGE FLOW ON SUNDAY. THIS IS NOT CERTAIN HOWEVER MOST GUIDANCE IS NOW INDICATING A MUCH DIFFERENT SCENARIO FOR SUNDAY WITH HIGHER CHANCES OF PRECIP GIVEN GOOD MOISTURE ADVECTION AND THE DEVELOPMENT OF LOW PRESSURE WAVES ALONG THE BOUNDARY. ALSO GIVEN THIS PATTERN MUCH COOLER TEMPS WOULD BE EXPECTED GIVEN FLOW OFF THE ATLC. HAVE NOT GONE NEARLY AS COOL AS THE 00Z GFS MOS TEMPS BUT HAVE DROPPED TEMPS SEVERAL DEGS NONETHELESS. LATER SHIFTS MAY NEED TO MAKE ADDITIONAL MAJOR CHGS TO THE SUNDAY FCST.

COLD FRONT IS STILL FCST TO MOVE QUICKLY ACROSS MON AND MON EVNG WITH VERY COOL AIR SURGING IN MONDAY NGT. TEMPS ON MONDAY DIFFICULT AND DEPENDANT ON TIMING OF FRONT. RETURN FLOW IN ADVANCE OF FRONT COULD SURGE WARM AIR ACROSS OUR AREA...HWVR GIVEN QUICK MOVEMENT OF COLD FRONT HAVE GONE WITH COOLER TEMPS ON MONDAY EXPECTING THE CLOUDS AND APPROACHING FRONT TO COUNTER ANY BRIEF BUT INTENSE WAA.

WILL CONTINUE TO MENTION PRECIP MIXING WITH SNOW SHWRS MON NGT...ALTHOUGH ACCUMULATIONS PROBABLY ONLY IN THE MTS. SOME UPSLOPE SN SHOWERS CONTINUE ON TUESDAY OTHERWISE A COOLER PATTERN SETS IN WITH TEMPS NEAR MID JAN NORMALS.

&&

.LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...NONE. &&

$$

SHORT TERM/HYDROLOGY/AVIATION/TIDES...ROGOWSKI LONG TERM...BROTHERTON MARINE...ROGOWSKI/BROTHERTON

.UPDATE... WATER VAPOR IMAGERY SHOWS A SHORTWAVE TRACKING THRU ONTARIO. AT THE SFC...ASSOCIATED BROAD SFC LOW APPEARS TO BE CENTERED OVER FAR NRN LAKE SUPERIOR. TROFFINESS HANGS BACK ACROSS NRN MN WITH ARCTIC AIR JUST TO THE N IN ONTARIO AND MANITOBA. FARTHER W...ARCTIC AIR IS SURGING S ACROSS THE DAKOTAS. UPPER DIVERGENCE IN RIGHT ENTRANCE OF JET ASSOCIATED WITH ONTARIO SHORTWAVE IS LEADING TO RADAR RETURNS IN NE MN...BUT HAVE NOT SEEN ANY SFC OBS INDICATING PCPN. LOW-LEVEL JET HAS SHIFTED E OF FCST AREA...AND WITH BAGGY PRES GRADIENT DEVELOPING...WINDS ARE DIMINISHING FROM W TO E THIS MORNING.

GOING FCST IS IN GOOD SHAPE FOR THE AFTN AND REQUIRES LITTLE IF ANY CHANGE. AS UPPER JET TRANSLATES E THIS AFTN...UPPER DIVERGENCE WILL ALSO SHIFT E. GIVEN THE RADAR RETURNS IN NE MN...IT IS NOT OUT OF THE QUESTION THAT A FEW -SHSN MAY DEVELOP OVER THE FAR W TOWARD EVENING. OTHERWISE...EXPECT A DRY AFTN. CLOUDS SHOULD GENERALLY HOLD TOUGH THRU THE AFTN...BUT VIS SATELLITE IMAGERY INDICATES CLOUDS ARE FAIRLY THIN ACROSS NRN WI INTO SRN UPPER MI. THIS MAY ALLOW TEMPS TO GET A COUPLE OF DEGREES HIGHER THAN 36-38F IN THE GOING FCST.

&&

.PREV DISCUSSION... ISSUED AT 330 AM EST

00Z RAOBS/LATEST WV IMAGERY AND RUC ANALYSIS SHOW WSW FLOW ALF BTWN DEEPENING TROF OVER THE PAC NW (12Z-24Z H3 HGT FALLS UP TO 200M THERE WITH SHRTWV DIGGING ALG THE PAC NW COAST) AND UPR RDG AXIS MOVING INTO SE ONTARIO. STRONG SHRTWV EMBEDDED WITHIN THIS FLOW IS MOVING INTO SRN MANITOBA...WITH ONLY WEAK SFC LO OVER ERN ND JUST NW OF FAR. STRONG ISENTROPIC ASCENT NOTED IN ADVANCE OF THIS SHRTWV... AND MQT VWP SHOWS S WINDS UP TO 55KT AT 3K FT MSL. GALE FORCE WINDS OBSVD OVER LK SUP FM ISLE ROYALE TO STANNARD ROCK. STRONG WAD HAS CONTRIBUTED TO EXTENSIVE MID CLD DECK OVER THE UPR GRT LKS...BUT DRY AIR SHOWN ON THE 00Z GRB RAOBS/ TAMDAR SDNG FM SAW BTWN H9-775 OR SO HAS RESTRICTED SN FOR THE MOST PART TO THE COLD SIDE OF H85 WARM FNT...LOCATED AT 00Z FM CKC-CMX-ERY...WHERE 0Z GFS F6 ALSO SHOWS SOME UPR DVGC. LTL IF ANY PCPN NOTED CLOSER TO THE SFC LO AND ALG ATTENDANT LO PRES TROF STRETCHING TO THE SW AS 00Z BIS/ABR/MPX SDNGS EXCESSIVELY DRY. MUCH COLDER AIR OBSVD OVER MT/ADJOINING AREAS IN SRN CAN.

MAIN FCST CONCERNS THIS PACKAGE ARE PCPN CHCS ASSOCIATED WITH SHRTWV/SFC LO TO THE WNW TDAY AND THEN DISTURBANCES IN WSW FLOW ALF IN THE WAKE OF THIS SHRTWV LATER AS VERY COLD AIR TO THE NW POISED TO MOVE INTO THE UPR GRT LKS.

FOR TDAY...NAM/GFS/UKMET SHOW SFC LO OVER NE MN THIS MRNG MOVING ACRS NRN LK SUP INTO SE ONTARIO BY 00Z AS SHRTV NR LK WINNIPEG SHEARS ENE ACRS ONTARIO...WITH ATTENDANT LO PRES TROF DRIFTING INTO THE CNTRL ZNS BY 00Z FRI. GIVEN EXCESSIVELY DRY AIRMASS UPSTREAM AT BIS/MPX/ ABR...PREFER THE DRIER NAM FCST (ZERO QPF) AS SHARPER ISENTROPIC LIFT/H85-5 QVECTOR CNVGC/LINGERING UPR DVGC/DEEPER MSTR EXIT EARLY THIS MRNG AND GIVE WAY TO DRYING ALF/H85-5 QVECTOR DVGC BY 18Z. IN FACT...GFS FCST SDNGS DEPICT THIS MID LVL DRYING QUITE WELL ABV INCREASINGLY SHALLOW MOIST LYR. TDAY WL BE WARMEST DAY OF NEXT WEEK AT LEAST AS SW FLOW IN ADVANCE OF APRCHG LO PRES TROF ADVECTS WARMER AIR FM THE SW...WHERE HI TEMPS REACHED NR 40 OR SRN MN ON WED...INTO THE FA.

GFS/UKMET/NAM SHOW A STRIPE OF HIER MID LVL RH DVLPG OVER THE NRN PLAINS THIS AFTN AND STREAKING ENE INTO THE WRN CWA LATE TDAY/TNGT/ FRI AS WAVES OF UPR DVGC IN RRQ OF H3 JET MAXES/SHRTWVS SHEARING ENEWD THRU WSW FLOW ALF IN CONFLUENCE ZN BTWN NRN/SRN BRANCHES AS WELL AS ACCOMPANYING H8-7 FGEN OVER RELATIVELY SHALLOW COLD AIR TO THE NW OF ARCTIC BNDRY NOW SEPARATING VERY COLD AIR IN MT/SRN CAN FM WARMER AIR STILL IN THE NRN PLAINS/MN THAT IS FCST TO GRDLY OOZE SE ACRS THE UPR LKS. THINK TRYING TO TIME EACH OF THESE WAVES WL BE FRUITLESS ATTM...SO WL CARRY CHC POPS ACRS MOST OF THE AREA THRU FRI TO ACCOUNT FOR THIS FGEN FORCING/POTENTIAL LES AS COLDER AIR GRDLY OVERSPRDS THE FA. IN GENERAL...WL GO WITH HIER CHC POPS TO THE NW EARLY IN THE PD AND GRDLY SHIFT THE HIER POPS TO THE SE AS ARCTIC BNDRY DRIFTS SLOWLY SE WITH TIME. RELATIVELY SHALLOW DEPTH OF COLD AIR AS WELL AS NEUTRAL-ALMOST ACYC LARGER SCALE LLVL FLOW WOULD SUG ANY LES WL BE ON THE LGT SIDE DESPITE ARRIVAL OF MUCH COLDER AIR BLO SHALLOW INVRN (GFS/NAM SHOW INVRN BASE TEMPS APRCHG -20C OVER THE NW BY LATE FRI). WL TEND TOWARD THE LO SIDE OF MOS GUIDANCE GIVEN HI STABILITY/SHALLOW NATURE OF ENCROACHING ARCTIC AIR.

ON FRI NGT/SAT...UPR CONFLUENCE ZN PROGGED TO PUSH FAR ENUF S THAT DRY ARCTIC HI PRES CENTER DRIFTS OVER THE FA. WL DIMINISH POPS TO NO HIER THAN 30 NR LK SUP ON LATE FRI NGT/SAT TO REFLECT INCRSGLY HOSTILE CONDITIONS FOR LES. MADE A FEW CHGS TO THE SAT NGT/SUN PD TO REFLECT TREND TOWARD MORE AGGRESSIVE NRN BRANCH THAT WL AT LEAST DELAY THE PROGRESSION OF THE SW UPR TROF TO THE NE. IN GENERAL CUT POPS A BIT DURING THIS TIME WITH GREATER INFLUENCE OF DRIER NRN BRANCH.

COORDINATED WITH GRB.

&&

.MQT WATCHES/WARNINGS/ADVISORIES...NONE. &&

$$

ROLFSON (UPDATE) KC (PREV DISCUSSION)

.DISCUSSION... 00Z RAOBS/LATEST WV IMAGERY AND RUC ANALYSIS SHOW WSW FLOW ALF BTWN DEEPENING TROF OVER THE PAC NW (12Z-24Z H3 HGT FALLS UP TO 200M THERE WITH SHRTWV DIGGING ALG THE PAC NW COAST) AND UPR RDG AXIS MOVING INTO SE ONTARIO. STRONG SHRTWV EMBEDDED WITHIN THIS FLOW IS MOVING INTO SRN MANITOBA...WITH ONLY WEAK SFC LO OVER ERN ND JUST NW OF FAR. STRONG ISENTROPIC ASCENT NOTED IN ADVANCE OF THIS SHRTWV... AND MQT VWP SHOWS S WINDS UP TO 55KT AT 3K FT MSL. GALE FORCE WINDS OBSVD OVER LK SUP FM ISLE ROYALE TO STANNARD ROCK. STRONG WAD HAS CONTRIBUTED TO EXTENSIVE MID CLD DECK OVER THE UPR GRT LKS...BUT DRY AIR SHOWN ON THE 00Z GRB RAOBS/ TAMDAR SDNG FM SAW BTWN H9-775 OR SO HAS RESTRICTED SN FOR THE MOST PART TO THE COLD SIDE OF H85 WARM FNT...LOCATED AT 00Z FM CKC-CMX-ERY...WHERE 0Z GFS F6 ALSO SHOWS SOME UPR DVGC. LTL IF ANY PCPN NOTED CLOSER TO THE SFC LO AND ALG ATTENDANT LO PRES TROF STRETCHING TO THE SW AS 00Z BIS/ABR/MPX SDNGS EXCESSIVELY DRY. MUCH COLDER AIR OBSVD OVER MT/ADJOINING AREAS IN SRN CAN.

MAIN FCST CONCERNS THIS PACKAGE ARE PCPN CHCS ASSOCIATED WITH SHRTWV/SFC LO TO THE WNW TDAY AND THEN DISTURBANCES IN WSW FLOW ALF IN THE WAKE OF THIS SHRTWV LATER AS VERY COLD AIR TO THE NW POISED TO MOVE INTO THE UPR GRT LKS.

FOR TDAY...NAM/GFS/UKMET SHOW SFC LO OVER NE MN THIS MRNG MOVING ACRS NRN LK SUP INTO SE ONTARIO BY 00Z AS SHRTV NR LK WINNIPEG SHEARS ENE ACRS ONTARIO...WITH ATTENDANT LO PRES TROF DRIFTING INTO THE CNTRL ZNS BY 00Z FRI. GIVEN EXCESSIVELY DRY AIRMASS UPSTREAM AT BIS/MPX/ ABR...PREFER THE DRIER NAM FCST (ZERO QPF) AS SHARPER ISENTROPIC LIFT/H85-5 QVECTOR CNVGC/LINGERING UPR DVGC/DEEPER MSTR EXIT EARLY THIS MRNG AND GIVE WAY TO DRYING ALF/H85-5 QVECTOR DVGC BY 18Z. IN FACT...GFS FCST SDNGS DEPICT THIS MID LVL DRYING QUITE WELL ABV INCREASINGLY SHALLOW MOIST LYR. TDAY WL BE WARMEST DAY OF NEXT WEEK AT LEAST AS SW FLOW IN ADVANCE OF APRCHG LO PRES TROF ADVECTS WARMER AIR FM THE SW...WHERE HI TEMPS REACHED NR 40 OR SRN MN ON WED...INTO THE FA.

GFS/UKMET/NAM SHOW A STRIPE OF HIER MID LVL RH DVLPG OVER THE NRN PLAINS THIS AFTN AND STREAKING ENE INTO THE WRN CWA LATE TDAY/TNGT/ FRI AS WAVES OF UPR DVGC IN RRQ OF H3 JET MAXES/SHRTWVS SHEARING ENEWD THRU WSW FLOW ALF IN CONFLUENCE ZN BTWN NRN/SRN BRANCHES AS WELL AS ACCOMPANYING H8-7 FGEN OVER RELATIVELY SHALLOW COLD AIR TO THE NW OF ARCTIC BNDRY NOW SEPARATING VERY COLD AIR IN MT/SRN CAN FM WARMER AIR STILL IN THE NRN PLAINS/MN THAT IS FCST TO GRDLY OOZE SE ACRS THE UPR LKS. THINK TRYING TO TIME EACH OF THESE WAVES WL BE FRUITLESS ATTM...SO WL CARRY CHC POPS ACRS MOST OF THE AREA THRU FRI TO ACCOUNT FOR THIS FGEN FORCING/POTENTIAL LES AS COLDER AIR GRDLY OVERSPRDS THE FA. IN GENERAL...WL GO WITH HIER CHC POPS TO THE NW EARLY IN THE PD AND GRDLY SHIFT THE HIER POPS TO THE SE AS ARCTIC BNDRY DRIFTS SLOWLY SE WITH TIME. RELATIVELY SHALLOW DEPTH OF COLD AIR AS WELL AS NEUTRAL-ALMOST ACYC LARGER SCALE LLVL FLOW WOULD SUG ANY LES WL BE ON THE LGT SIDE DESPITE ARRIVAL OF MUCH COLDER AIR BLO SHALLOW INVRN (GFS/NAM SHOW INVRN BASE TEMPS APRCHG -20C OVER THE NW BY LATE FRI). WL TEND TOWARD THE LO SIDE OF MOS GUIDANCE GIVEN HI STABILITY/SHALLOW NATURE OF ENCROACHING ARCTIC AIR.

ON FRI NGT/SAT...UPR CONFLUENCE ZN PROGGED TO PUSH FAR ENUF S THAT DRY ARCTIC HI PRES CENTER DRIFTS OVER THE FA. WL DIMINISH POPS TO NO HIER THAN 30 NR LK SUP ON LATE FRI NGT/SAT TO REFLECT INCRSGLY HOSTILE CONDITIONS FOR LES. MADE A FEW CHGS TO THE SAT NGT/SUN PD TO REFLECT TREND TOWARD MORE AGGRESSIVE NRN BRANCH THAT WL AT LEAST DELAY THE PROGRESSION OF THE SW UPR TROF TO THE NE. IN GENERAL CUT POPS A BIT DURING THIS TIME WITH GREATER INFLUENCE OF DRIER NRN BRANCH.

COORDINATED WITH GRB.

&&

.MQT WATCHES/WARNINGS/ADVISORIES... GALE WARNING E HALF LAKE SUPERIOR UNTIL 8 AM EST. &&

$$ KC

.DISCUSSION...LAKE EFFECT SNOW SHOWERS CONTINUE OVER THE SOUTH SHORE...MAINLY ACROSS IRON AND FAR NORTHEAST ASHLAND COUNTIES. 00Z INL AND A TAMDAR SOUNDING AT DLH THIS EVENING SHOW INVERSION AT OR BELOW 2000 FEET...BUT FORECAST SOUNDINGS NEAR KIWD ARE ABOUT 1000 FT HIGHER AND THAT SEEMS REASONABLE WITH THE LAKE SUPERIOR INFLUENCE. DELTA-T`S FAVORABLE...AND ARE AROUND -19C OR -20C.

WE HAVE ALREADY HAD 5 TO 7 INCHES REPORTED IN SPOTS AROUND HURLEY AND MONTREAL...AND MUCH OF THAT FELL DURING THE DAY...AND WE COULD STILL SEE ANOTHER 2 TO 4 INCHES TONIGHT WITH GOOD NORTHERLY FLOW. WE WILL ISSUE AN ADVISORY FOR ASHLAND AND IRON COUNTY TONIGHT...THROUGH 6 AM. INVERSION LEVELS AND FLOW WEAKENS...THEN VEERS AROUND TO WEST TO SOUTHWEST AFTER 6 AM.

&&

POINT TEMPS/POPS... DLH -11 11 -1 13 / 10 10 10 20 INL -25 2 -11 2 / 10 10 20 20 BRD -12 11 -1 13 / 10 10 10 10 HYR -8 16 2 19 / 10 10 20 20 ASX -5 16 4 16 / 60 20 20 40

&&

.DLH WATCHES/WARNINGS/ADVISORIES...

MN...NONE. WI...LAKE EFFECT SNOW ADVISORY UNTIL 6 AM CST SATURDAY FOR ASHLAND- IRON.

LS...NONE.

$$

MELDE

.DISCUSSION...

&&

PREV DISCUSSION... /ISSUED 410 PM CST WED JAN 10 2007/

DISCUSSION... THROUGH SATURDAY...A WEDGE OF ARCTIC AIR PUSHES SOUTHWARD FROM BRITISH COLUMBIA ON THE BACKSIDE OF A DEEP LOW PRESSURE SYSTEM PASSING OUT OF THE EASTERN DAKOTAS. HOWEVER...THE COLDER THICKNESS FIELD OVER CENTRAL CANADA REALLY DOES NOT CONNECT WITH THIS SOUTHWARD PUSH OF COLD AIR. IN FACT THE CENTROID OF ARCTIC AIR IS STILL ON THE WEST END OF HUDSON BAY LATE SATURDAY (BASIS NAM80 RUN FROM 12Z THIS MORNING) AND THE BAROCLINITY TO THE SOUTH OF THIS POOL OF ARCTIC AIR STAYS NORTH OF THE US BORDER.

AFTER SATURDAY...SOUTHWEST FLOW ALOFT A TROUGH OVER THE WESTERN US INDUCES A EXTRATROPICAL CYCLONE TO FORM OVER UTAH/COLORADO AND THIS SYSTEM EJECTS ACROSS THE MID MISSISSIPPI VALLEY THROUGH SUNDAY. WE MODELED OUT PRECIPITATION GRIDS ON THE BASIS OF THE GFS ENSEMBLES WHICH CARRIES THE MAIN THREAT FOR LIGHT SNOW ACROSS OUR SOUTHERNMOST MN COUNTIES. WE ALSO CARRY A SMALL RISK FOR LIGHT SNOW IN OUR SOUTHEAST CWA COUNTIES THURSDAY NIGHT BUT THIS MAY REALLY BE A STRETCH SO LATER SHIFTS WILL HAVE TO ASSESS THIS RISK.

AVIATION...UPDATE FOR 00Z TAF CYCLE WINDS WILL SLACKEN FAIRLY QUICKLY THROUGH THIS EVE WITH PRIMARY TAF CONCERN BECOMING CIGS LATE TONIGHT AND INTO THURS. LATEST SFC ANALYSIS HAS A FAIRLY BROAD AREA OF LOW PRESSURE IN ERN SD. THIS WILL TRAVERSE ACROSS CTRL MN TONIGHT. UNDER THIS...LOW LEVEL MOISTURE IS FAIRLY HIGH REPRESENTED BY SFC TDS AND LAPS SOUNDINGS. TEMPERATURE COMPARISON BETWEEN THE BOUNDARY LAYER AND THE SURFACE FAVOR STRATUS FORMATION MORESO THAN ANY FOG. SO CONTINUE TO MENTION STRATUS NEAR DAWN AND INTO THURS MORNING FOR WRN MN TAF SITES. THERE IS A POSSIBILITY OF MVFR CIGS MOVING INTO STC AND MSP DURING LATE THURS MORN AND INTO THE AFTN...BUT CONFIDENCE IS NOT HIGH ENOUGH AT THIS TIME. ARCTIC FRONT WILL WORK ITS WAY INTO WRN MN JUST BEYOND TAF CYCLE AND PRESENT MORE ENHANCED LOW CLOUD THREAT.

&&

.AVIATION...UPDATE FOR 06Z TAF CYCLE CHALLENGE WITH TAFS ARE POSSIBILITIES OF FOG OR STRATUS THROUGH THURS MORNING. LATEST HAND SFC ANALYSIS PLACED BROAD SFC LOW IN FAR WESTERN MN WITH SFC WARM FRONT EXTENDING ALONG MN RIVER VALLEY. WARM FRONT SHOULD LIFT SLIGHTLY FURTHER NORTH THROUGH MORNING WITH LOW LEVEL FLOW TO THE SOUTH LIKELY PREVENTING ANY FOG OR STRATUS DEVELOPMENT. AS FOR UNDERNEATH THE LOW...WHICH WILL TRAVERSE ACROSS AXN...STC...AND NORTHERN SATELLITE AIRPORTS OF MSP THRU DAWN...SLACKENING FLOW AND SFC TDS NEAR 30F OFFERING STRATUS OR FOG THREAT. THERMAL PROFILE FROM RECENT TAMDAR SOUNDING AND BUFKIT SOUNDINGS INDICATING AXN AND STC HAVE THE BEST POSSIBILITY FOR FOG BETWEEN HOLES IN MID LEVEL CLOUDS. MSP OBSERVED AND PROGGED PROFILE HAVE A STRONGER INVERSION ALOFT AND MORE CONDUCIVE THEREFORE FOR STRATUS. COULD BE SOME MVFR CIGS FROM DAWN THROUGH MID MORNING BUT POSSIBILITY NOT STRONG ENOUGH TO MENTION. WINDS WILL TURN NWRLY ON THURS AFTN WITH ARCTIC FRONT ENTERING MN TOMORROW EVE. THIS WILL LIKELY BE THE BEARER OF COLD AIR ADVECTION STRATOCU CLOUDS.

.MPX WATCHES/WARNINGS/ADVISORIES... MN...NONE. WI...NONE. &&

$$

.EVENING UPDATE... 820 PM CST

ZFP/GRIDS/WSW OUT. FOCUS OF THIS UPDATE WAS ON RAIN FALLING ACROSS SOUTHERN CWA. CALLS TO LIVINGSTON...FORD...AND LA SALLE COUNTY IN THE PAST HR OR SO INDICATE NO ICING PROBLEMS. PNT/TIP/IKK STILL ABOVE FREEZING AND REPORTING RAIN. COLD AIR WILL SLOWLY SINK SOUTH AND EXPECT RAIN TO SLOWLY CHANGEOVER TO FREEZING RAIN EVENTUALLY. BUT BY THE TIME IT DOES MAKE A CHANGE...QPF AMOUNTS WILL BE LIGHT. INDICATED UP TO ONE TENTH OF AN INCH OF ICE IN THE WSW ACROSS THIS AREA...BUT THIS WILL BE ISOLATED. WITH CHANGEOVER OCCURRING LATER... PUSHED FREEZING RAIN ADVISORY TO 12Z ACROSS THE SOUTHERN HALF OR SO OF THE CWA.

FURTHER NORTH...ADVISORY EXPIRED FOR NW IL AND THAT LOOKS ON TRACK. WAS RELUCTANT TO PULL ADVISORY FOR NE IL THOUGH AREAS NORTH OF I-88 APPEAR TO STAY MAINLY DRY THRU THE NIGHT. THOUGH ORD IS REPORTING -DZ THIS HR AND -RA AT MDW. WHILE SFC TEMPS REMAIN ABOVE FREEZING HERE...TEMPS COULD DIP BELOW FREEZING BEFORE 2AM. SINCE THE ADVISORY WAS ALREADY OUT...DECIDED TO LET IT RIDE FOR NOW...BUT PRECIP WILL BE LIGHT AND IMPACTS SHOULD BE SMALL.

&&

.PREVIOUS DISCUSSION... 400 PM CDT

THE FIRST ISSUE IS THE FREEZING RAIN TONIGHT. WE HAVE ADVISORY FOR ALL OF THE CWA AT ONE TIME OR ANOTHER. THE COLD FRONT WAS FROM GARY INDIANA TO ST LOUIS AT 19 UTC. AS THE COLD AIR MOVES INTO NORTHEAST ILLINOIS AND NORTHWEST INDIANA...WARM AIR OVERRIDES IT AND THIS CREATES PRECIPITATION. USING A CROSS SECTION OF EQUIVALENT POTENTIAL TEMPERATURE WE SEE THAT THIS COLD AIR IS SHALLOW. UP TO THE 800 MB LEVEL. ACARS SOUNDINGS AT ORD SHOWS THE AIR ABOVE FREEZING UP TO 737 MB. WEST OF A LINE FROM BOONE MCHENRY BORDER TO EASTERN FORD COUNTY THE DRIZZLE AND FREEZING RAIN HAS BEGUN. EAST OF THAT LINE THE TEMPERATURE HAS NOT FALLEN BELOW 0 DEGREES C NEAR THE SURFACE AND UP TO 800 MB YET.

THE FORECAST SOUNDING FROM THE LOCALLY RUN WRF ARW MODEL SHOWS A LAYER OF THE ATMOSPHERE FROM 896 MB TO 716 MB ABOVE FREEZING. ABOVE THAT THE MOISTURE IN THE AIR IS NEARLY IN EQUILIBRIUM WITH THE VAPOR PRESSURE OF WATER. THIS IS AROUND PONTIAC. THERE MAY BE SOME ICE CRYSTAL FORMING AND SO WE WILL ADD ICE PELLETS FOR BENTON COUNTY INDIANA TONIGHT. OTHERWISE WE WILL FORECAST DRIZZLE AND FREEZING RAIN TONIGHT UP TO AROUND 2 AM. AFTER 06 UTC THE ISENTROPIC LIFT ON THE 285K SURFACE DECREASES AND THERE WILL BE COLD AND DRIER AIR INTO THE REGION.

THE SNOW STORM ON SUNDAY THROUGH MONDAY WILL BE THE NEXT WEATHER EVENT. WE USED THE GFS...NAM AND NGM MODELS FOR THIS FORECAST. A CYCLONE IS FORECAST TO DEVELOP IN TEXAS. 850 MB AND 1000 MB TEMPERATURE GRADIENTS AND TEMPERATURE ADVECTION ARE OPERATED ON BY A LAPLACIAN AND INTEGRATED UP TO 850 MB SHOW INCREASE IN LOW LEVEL VORTICITY OVER ARKANSAS BY 00 UTC MONDAY. A LOW WILL DEVELOP THERE AND MOVE INTO KENTUCKY BY 06 UTC MONDAY. THE TRACK OF THE 850 MB TROUGH AND Q VECTORS PUT AN AREA OF LIFT MOVING FROM SOUTHEAST IOWA AND MOVES IT THROUGH CHICAGO BY 12 UTC MONDAY. THIS WILL PROVIDE SOME FORCING FOR SNOW SUNDAY NIGHT AND EARLY MONDAY MORNING. THICKNESS FORECAST SHOW THE SOUTHERN THIRD OF THE FORECAST AREA WILL HAVE SOME MIXED PRECIPITATION FREEZING RAIN AND ICE PELLETS. THERE IS ENOUGH MOISTURE ABOVE -12 DEGREES CELSIUS THAT ICE CRYSTALS WILL FORM AND FALL. THERE MAY BE SUPERCOOLED WATER DROPS AS WELL SUNDAY AND SUNDAY AFTERNOON. BY SUNDAY NIGHT THE WHOLE COLUMNOF AIR MAY BE COLD ENOUGH FOR SNOW. WE WILL FORECAST ALL SNOW SUNDAY NIGHT INTO MONDAY. THIS STORM EVENT WILL END MONDAY AFTERNOON. THE LOW WILL MOVE INTO PENNSYLVANIA. WE EXPECT ABOUT 4 TO 7 INCHES OF SNOW FOR THE WHOLE AREA BY MONDAY AFTERNOON AT THIS TIME.

&&

.AVIATION... 1045 PM CST

RE THE 06Z TAFS...CDFNT CONTS TO PUSH SEWRD INTO LWR GRTLKS AND LWR OH VALLEY. STRONGEST PUSH OF LLVL COLD AIR THIS EVE HAS BEEN SWRD FM THE UPR MIDWEST AND NRN PLAINS AND ACROSS NW INTO W CNTRL IL. THIS HAS RESULTED IN SIGNIFICANT ICING FM MO NEWRD INTO CNTRL IL...WHILE FURTHER TO THE E SFC TEPS STILL ABV FREEZING SO JUST RA FALLING. PROFILERS AND 00Z RAOBS SHOWING 40KT FEED OF GULF MOISTURE INTO THE BAROCLINIC ZONE CURRENTLY LAYING OUT SW-NE FM MO INTO THE NRN OH. AS THIS ZONE SAGS SWRD THE NRN EDGE OF THE PRECIP WILL ALSO SAG S AND OUT OF TERMINALS DURG THE NEXT FEW HRS. PRECIP EXPECTED TO START TO RETURN NWRD LATE SAT AFTERNOON AND SPREAD TO TERMINALS DURG SAT EVE AS WRN U.S. UPR GRADUALLY MOVS TO ROCKIES INDUCING THE MID LVL FLO TO BACK A BIT. BETWEEN END OF PRECIP LATE TONIGHT AND RETURN ON SAT EVE EXPECT CIGS TO LIFT TO PREVAILING MVFR AS LOER SFC DWPTS FEED IN ON N TO NE WNDS.

TRS

&&

.LOT WATCHES/WARNINGS/ADVISORIES... .IL...FREEZING RAIN ADVISORY MCHENRY LAKE COOK DUPAGE KANE KENDALL WILL UNTIL 08Z. FREEZING RAIN ADVISORY LASALLE GRUNDY KANKAKEE LIVINGSTON FORD IROQUIOUS UNTIL 12Z. .IN...FREEZING RAIN ADVISORY LAKE AND PORTER UNTIL 08Z. FREEZING RAIN ADVISORY NEWTON JASPER BENTON UNTIL 12Z. .LM...SMALL CRAFT ADVISORY FOR ALL NEAR SHORE UNTIL 15Z.

&&

$$

.SHORT TERM (TODAY AND TONIGHT)...

CURRENTLY...DEEP SWRLY FLOW IS DOMINATING ACROSS THE REGION. A COLD FRONT IS QUICKLY APPROACHING FROM THE WEST AND IS PUSHING THROUGH EVV ATTM. LOW-LEVEL COLD AIR IS FILTERING IN BEHIND THE FRONT FASTER THAN MODELS HAD ANTICIPATED. LARGE AMOUNT OF ISENTROPIC LIFT OVER THE COLD AIR HAS LED TO QUITE AN ICING EVENT OVER PORTIONS OF OK INTO MO. LARGE TEMP GRADIENT PRESENT AS WELL...AS PAH WAS AT 60 DEGREES AND CAPE GIRARDEAU AT 39 DEGREES AT 2AM EST.

DESPITE COLD FRONT QUICKLY APPROACHING...A LOW PRESSURE WAVE OVER THE TEXARKANA REGION RIDING NEWD ALONG THE FRONT WILL HELP SLOW THE FRONT`S PROGRESSION...AND WILL BE RESPONSIBLE FOR OUR FIRST WAVE OF POTENTIALLY HEAVY PRECIP...WHICH IS CURRENTLY OVER WRN KY. THIS AREA SHOULD EXPAND AND FILTER INTO OUR CWA THROUGHOUT THE MORNING. MAY EVEN SEE A RUMBLE OF THUNDER OR TWO WITH THIS FIRST BATCH OF RAINFALL GIVEN UPSTREAM TRENDS. WILL ONLY MENTION ISLD THREAT WEST OF I-65 THIS MORNING. AFTER THIS MORNING`S MAIN AREA OF PRECIP...A LULL IN THE PRECIP SHOULD OCCUR THIS AFTERNOON BEFORE ANOTHER LOW PRESSURE WAVE RIDES NEWD ALONG THE FRONT TONIGHT...CAUSING ANOTHER BOUT OF POTENTIALLY HEAVY RAIN.

THOUGH RAIN ONSET IS LATER THAN ANTICIPATED...STILL THINK THE FLOOD WATCH IS WARRANTED THROUGH THE WEEKEND. PWATS ARE OVER AN INCH NOW...AND NAM BUFKIT SOUNDINGS INDICATE NEAR 1.5 INCHES THIS EVENING...WHICH IS SUPPORTED BY THE 4-5 STD DEVIATIONS ABV NORMAL POSED BY THE SHORT-RANGE ENSEMBLES. ALSO...NAM AND GFS INDICATE SOME ELEVATED INSTABILITY WITH LI`S AROUND ZERO TONIGHT...WHICH WILL AID IN OVERALL PRECIP AMOUNTS GIVEN THIS CONVECTION. STILL THINK SOME LOCATIONS COULD SEE 2-3 INCHES OF RAINFALL...WITH ISOLATED LOCATIONS SEEING 4 INCHES OR MORE. HOWEVER...GIVEN THE SLOW ONSET THINK A WIDESPREAD FLOODING EVENT IS NOT LIKELY...THOUGH A MINOR AND MORE ISOLATED FLOODING EVENT IS CERTAINLY POSSIBLE...SO WILL CONTINUE FLOOD WATCH. MAY DOWN PLAY AMOUNTS A WEE BIT BUT THAT IS ALL.

THE FRONT WILL BE CLOSELY ALIGNED WITH THE OHIO RIVER AROUND SUNRISE AND SHOULD BE IN NEARLY THE SAME LOCATION OR JUST SE BY MIDNIGHT TONIGHT. WILL KEEP CATEGORICAL POPS GOING...WITH MENTION OF LOCALLY HEAVY RAINFALL.

FOR AVIATION CONCERNS...HAVE LOW-LEVEL WIND SHEAR IN ALL THE TAF SITES THIS MORNING GIVEN THE STRONG SWRLY JET OF 40-45 KTS OVER THE CWA NOW...EVIDENT FROM AREA VWPS AND SDF ACARS SOUNDINGS. MAY SEE SOME GUSTY WINDS HERE AND THERE...BUT NOTHING OUT OF HAND AS CLOUDY SKIES SHOULD HELP INHIBIT LARGER GUSTS.

TEMPS WILL BE TRICKY TODAY...AND COULD HAVE QUITE THE GRADIENT ACROSS THE CWA...ESPECIALLY BY MIDDAY. TEMPS MAY DROP AND/OR STEADY OUT ACROSS THE NW...WITH CURRENT READINGS IN THE UPPER 50S DROPPING TO THE UPPER 40S AND HOLDING THERE. THE SERN CWA COULD SEE HIGHS A FEW DEGREES WARMER THAN CURRENT READINGS...AND SHOULD STICK AROUND 60 FOR THE MOST PART. OVERNIGHT LOWS WILL NOT BUDGE MUCH AND SHOULD BE JUST A FEW DEGREES COLDER THAN HIGHS TODAY.

AL

.LONG TERM (SUNDAY THROUGH FRIDAY)...

SUNDAY AND MONDAY...

FORECAST CHALLENGE WILL BE PLACEMENT OF THE COLD FRONT AT THE BEGINNING OF THIS PERIOD. LATEST SHORT RANGE MODELS DID NOT INITIALIZE SHALLOW COLD AIR WELL AND FEEL IT WILL BE FURTHER SOUTH THAN MODELS SUGGEST. SURFACE WAVE SHOULD SHIFT THE COLD AIR NORTH SOME DURING THE AFTERNOON SUNDAY AND AT THIS TIME WE WILL KEEP PRECIPITATION ACROSS THE NORTH IN THE FORM OF RAIN. THE AXIS OF HEAVY RAIN SUNDAY AND SUNDAY NIGHT STILL LOOKS TO BE ALONG THE OHIO RIVER WHERE AN INCH TO AN INCH AND A HALF WILL BE POSSIBLE. LIGHTEST AMOUNTS WILL OCCUR ACROSS THE SOUTHEAST PORTION OF THE COUNTY FORECAST AREA. WE WILL HOLD ONTO ISOLATED THUNDERSTORMS SOUTH OF THE OHIO RIVER SUNDAY WHERE BEST DYNAMICS EXIST...ALTHOUGH INSTABILITY WILL BE LACKING.

TEMPERATURES WILL BE A CONCERN AS WELL AS A 10 TO 15 DEGREE GRADIENT WILL BE NOTED ACROSS THE COLD FRONT. HIGHS SUNDAY WILL TOP OUT IN THE LOWER 40S ACROSS SOUTHERN INDIANA WITH UPPER 50S EXPECTED NEAR THE TENNESSEE BORDER.

ONCE THE SURFACE LOW MOVES NORTHEAST OF THE REGION THE MODIFIED ARCTIC AIR WILL ENTER THE FORECAST AREA MONDAY. HIGHEST TEMPERATURES WILL OCCUR DURING THE MORNING. LIGHT SNOW SHOWERS WILL BE POSSIBLE MONDAY BUT NO ACCUMULATION IS EXPECTED.

JA

TUESDAY THROUGH FRIDAY...

NOT MUCH CHANGE IN THE FORECAST THROUGH THIS TIME PERIOD. WITH FRONT CONTINUING TO OUR SOUTH AND HIGH PRESSURE BUILDING IN FROM THE UPPER PLAINS...NORTHERLY WINDS WILL GET THE LAKE-EFFECT SNOW MACHINE GOING TO OUR NORTH. DOWN THIS FAR SOUTH...FEEL THAT SCT FLURRIES WILL BE POSSIBLE DURING THE DAY ON TUESDAY AND WILL LEAVE AS SUCH. BETTER CHC FOR SNOW SHOWERS WOULD EXIST OVER FAR EAST KY IN THE FAVORED UPSLOPE REGIONS. DRY FORECAST IS ANTICIPATED FOR WEDNESDAY THROUGH FRIDAY AS HIGH PRESSURE CONTINUES TO BUILD OVER THE REGION. TEMPERATURES AT THE BEGINNING OF THIS PD WILL BE WELL BELOW NORMAL WITH HIGHS IN THE UPPER 20S TO LOWER 30S AND OVERNIGHT LOWS IN THE UPPER TEENS. SOME MODERATION IN THE TEMPERATURES WILL OCCUR BY THURSDAY AND FRIDAY WITH TEMPERATURES WARMING SLIGHTLY INTO THE MID AND UPPER 30S. GENERALLY STUCK CLOSE TO THE HPC GUIDANCE THROUGH THIS PERIOD.

MJ

&&

.LMK WATCHES/WARNINGS/ADVISORIES... KY...FLOOD WATCH THROUGH LATE SUNDAY NIGHT FOR KYZ023>043-045>049- 053>057-061>067-070>078-081-082.

IN...FLOOD WATCH THROUGH LATE SUNDAY NIGHT FOR INZ076>079-083-084- 089>092.

&&

$$

.DISCUSSION...

...MAIN CONCERN THIS MORNING CONTINUES TO BE POTENTIAL HVY SNOWFALL SUNDAY NIGHT INTO MONDAY MORNING BUT NO HEADLINES FOR NOW...

COMPLEX SITUATION EVOLVING OVER THE NEXT 72 HRS AND MODELS THIS MORNING ARE NOT IN TOO GOOD AGREEMENT. HOWEVER...WILL PUSH THRU THE DIFFERENCES AND HOPE TO ARRIVE AT THE MOST LIKELY SCENARIO.

IN THE SHORT TERM...FIRST WAVE PULLING OUT WITH PRECIP SLOWLY ENDING FROM WEST TO EAST ACROSS THE SOUTHERN HALF OF THE CWA. PRECIP HAS REMAINED PREDOMINANTLY RAIN AND WHERE PRECIP HAS CHANGED OVER TO A MIX...IT HAS BEEN LIGHT WITH A SHORT DURATION. WILL CONTINUE TO WATCH RADAR TRENDS BUT EXPECT THE BULK OF THE PRECIP TO BE OUT OF ALL BUT THE FAR SE CWA BY DAWN AND PLAN TO CARRY JUST A CHANCE OF LIGHT RAIN OR DRIZZLE ACROSS THE SOUTH THIS MORNING AND SHOULD BE ABLE TO CANCEL THE REST OF THE -FZRA ADVISORY WITH MORNING ZFP. WILL ALSO CARRY -DZ/-FZDZ THIS MORNING WITH A FEW LOCATIONS STILL REPORTING MIXED PRECIP.

TEMPS CLIMB A FEW DEGREES FROM AM LOWS GENERALLY IN THE LOWER 30S NORTH TO UPPER 30S SE. NEXT WEAK WAVE ARRIVES TONIGHT AND DESPITE LIKELY POPS OFF GUIDANCE...QPF AMOUNTS ARE RATHER LIGHT. LOOKING AT THE SOUNDINGS AND THERMAL PROFILES AND WARMER SFC TEMPS...THINK THE SOUTHERN PART OF THE CWA MAY REMAIN JUST RAIN WITH A MIX ACROSS THE MIDDLE PART OF THE CWA TO SNOW NORTH. WILL MODIFY FORECAST ALONG THESE LINES. DEPENDING ON HOW MUCH MIXED PRECIP OCCURS...AN ADVISORY MAY BE NEED AGAIN FOR TONIGHT BUT WILL HOLD OFF ON HEADLINES. PRECIP TAPERS OFF SUNDAY MORNING WITH ANOTHER LULL DURING THE DAYLIGHT HRS AND HAVE BACKED OFF TO CHANCE POPS.

THEN COMES THE MAIN SHOW SUNDAY NIGHT. HAVE WATCHED THE MODELS FOR THE PAST 4 DAYS WITH THIS SYSTEM. SOME HIGHLIGHTS INCLUDE THE GFS BEING RATHER CONSISTENT WITH A MORE SOUTHERLY AND WEAKER TRACK OF THE SFC LOW. THE NAM REMAINING FURTHER NORTH OF THE GFS ON EVERY RUN...TRYING TO TREND TOWARD THE GFS A FEW DAYS AGO BUT NOW BACK TO A DEEPER AND FARTHER NORTH TRACK AND EVEN SHOWING SOME SIGNS OF TRYING TO BECOME NEGATIVELY TILTED. BY 12Z MONDAY THE GFS IS THE FARTHEST SE WITH THE UKMET NEARBY AND THE ECMWF/CANADIAN SLIGHTLY MORE NORTH BUT NOT AS MUCH AS THE NAM...THOUGH THEY ARE A LITTLER FARTHER NORTH THEN PREVIOUS RUNS. WITH HIGH PRESSURE ACROSS THE PLAINS BEGINNING TO WEAKEN AND RAPIDLY WEAKENING TODAY/TONIGHT... DOUBT COLD FRONT WILL MOVE MUCH FARTHER SOUTH AND WILL LIKELY BECOME STATIONARY THIS MORNING FARTHER NORTH THAN MODELS SUGGEST. SFC LOW WILL RIDE CLOSE TO THIS BOUNDARY AND AS A RESULT PREFER THE NAM STRENGTH AND FARTHER NORTH TRACK...THOUGH FINAL TRACK MAY END UP CLOSER TO MODEL CONSENSUS. ALSO PREFER SLIGHTLY SLOWER TIMING. A QUICK LOOK AT THE 06Z NAM LOOKS VERY SIMILAR TO THE 00Z RUN.

WITH THIS IN MIND...PRECIP DEVELOPS LATE SUNDAY AFTERNOON AND SPREADS NE ACROSS THE ENTIRE AREA SUNDAY EVENING. PLENTY OF MOISTURE FOR THIS SYSTEM TO WORK WITH AND A PERIOD OF SNOW... POSSIBLY HEAVY SNOW...ACROSS THE NORTHERN TWO THIRDS OF THE CWA LOOKS GOOD...TAPERING OFF TO FLURRIES AFTER SUNRISE MONDAY MORNING. PROBLEM FURTHER SOUTH WILL BE PRECIP TYPE. NOT SURE EVEN MDT/HVY PRECIP COULD OVERCOME LARGE DEPTH OF WARM AIR...AT LEAST IN THE WARMEST SCENARIO AND WILL KEEP A MIX OF PRECIP SOUTH OF A LINE FROM PNT TO GYY...WHICH WILL KEEP SNOW AMOUNTS LOWER THERE. GOING FORECAST INDICATES 6+ INCHES NORTH OF A LINE FROM GYY/PNT. SEE LITTLE REASON TO DEVIATE FROM THIS FORECAST. HOWEVER...HAVE DECIDED TO HOLD OFF ON A WATCH THIS MORNING FOR A FEW REASONS. DESPITE PREFERENCE TO THE NAM...IT IS THE FARTHEST NORTH. MIXED PRECIP TONIGHT MAY NEED AN ADVISORY AND A WATCH FOR 4TH PERIOD MAY CONFUSE OR CAUSE 2ND PERIOD POTENTIAL PROBLEMS TO BE OVERLOOKED. SO WILL DEFER WATCH/ADVISORY TO THE DAY SHIFT AND HOPEFULLY THE MODELS WILL SHOW A CLEARER PICTURE.

AS FOR LAKE ENHANCEMENT AND LAKE EFFECT...WATER TEMPS IN THE UPPER 30S OR +3C TO +4C. DURING THE MAIN SNOW SUNDAY NIGHT...THERE MAY BE SOME ENHANCEMENT BUT IT APPEARS MINIMAL AT THIS POINT. 850MB TEMPS REALLY DON/T DROP OFF UNTIL MONDAY AFTERNOON FOR FAVORABLE LAKE EFFECT AND THEN CONTINUE TO DROP MONDAY NIGHT INTO TUESDAY AS WINDS TURN MORE NORTH AND NORTHWEST. AM MORE CONCERNED ABOUT LAKE EFFECT SNOW DURING THIS TIME WHEN DELTA T`S REACH 20 DEGREES BY TUESDAY AFTERNOON WITH INVERSION HEIGHTS OF 7-8KFT. FOR NOW WILL INCLUDE CHANCE OF SNOW SHOWERS BUT THIS TOO WILL NEED TO BE WATCHED FOR ACCUMULATING SNOW...ESPECIALLY ACROSS NORTHWEST INDIANA.

&&

.AVIATION DISCUSSION REGARDING 12Z TAFS...

CURRENT SATLT IMAGERY SHOWS EXTENSIVE CLOUD DECK OVER THE MIDWEST ASSD WITH A DAMPENING SHORT WAVE TROF NOW EJECTING ENEWD ACRS THE MID MS VLY. PCPN WITH THIS FEATURE HAS SHIFTED S AND E OF THE TERMINAL AREA. THERFORE...EXPECT TDY TO BE GENLY FREE OF PCPN WITH NO VIS RESTRICTIONS. WILL KEEP CIGS IN MVFR RANGE. SFC OBS PAST SVRL HRS HAVE SUGGESTED PERSISTENT NELY FLOW BLO FRONTAL INVERSION (BLO ABOUT 25 HND FT BASED ON ACARS) HAS ERODED AWAY LOWER CLOUDS. THIS WILL CONTINUE THRU TDY AS NELY LLVL FLOW CONTS TO ADVECT LOW DEW POINT AIR FROM SRN WI/LWR MI INTO RGN.

NXT WX PROBLEM FCST TO ARRIVE TNGT. SATLT LOOPS SHOW ANOTHER MINOR DISTURBANCE LIFTING NEWD FROM WRN TX ERLY THIS MRNG. THE FACT THAT IT IS TRIGGERING THUNDER AS FAR N AS THE TX PHDL SUGGESTS IT IS A FAIRLY DYNAMIC LITTLE FEATURE. AS THIS WAVE REACHES THE MIDWEST THIS EVENING...SOME LIGHT PCPN IS EXPECTED TO OVERSPREAD THE RGN...MAINLY IN 03Z-09Z TIME FRAME. FCST SOUNDINGS SUGGEST PCPN WILL BE LGT SNOW RFD-ORD-DPA AREAS...WITH SOME ICE PELLETS MDW-ARR-PNT AND RAIN/FZRA/ICE PELLETS VPZ-IKK. AGAIN...THIS IS EXPECTED TO BE A MINOR EVENT...BUT CIGS/VIS WILL LIKELY LWR TO IFR AGN OVERNGT.

MERZLOCK

&&

.LOT WATCHES/WARNINGS/ADVISORIES... .IL...NONE. .IN...NONE. .LM...SMALL CRAFT ADVISORY FOR ALL NEAR SHORE UNTIL 15Z.

&&

$$

.MORNING UPDATE (THIS AFTERNOON/TONIGHT)...

CURRENT MORNING SFC ANALYSIS REVEALS COLD FRONT FROM NEAR CMH SW TO JUST WEST OF MEM. PRETTY GOOD TEMPERATURE GRADIENT NOTED ACROSS THE FAR NW PORTION OF THE DISTRICT WITH READINGS IN THE MID AND UPPER 50S ACROSS MUCH OF THE FA...BUT UP NEAR JASPER TEMPERATURES HAVE DROPPED INTO THE MID 40S. AREA RADARS SHOWING NEXT ROUND OF LIGHT TO MODERATE RAIN MOVING IN FROM THE WEST WHICH WILL PASS THROUGH THE FA THIS AFTERNOON. EASTERN SECTIONS WILL SEE A GENERAL DOWNWARD TREND IN PRECIPITATION LATE THIS MORNING BEFORE INCREASING AGAIN IN THE AFTERNOON.

LOOKING AT THE LATEST SHORT TERM GUIDANCE...THE RUC MODELS (13KM/40KM) SEEM TO HAVE A VERY GOOD HANDLE ON TEMPERATURES THIS MORNING. THE RUC MODELS SEEM TO BRING THE FRONT TO ABOUT LOUISVILLE LATE THIS EVENING AND THEN STALLING IT OUT. THE NET RESULT WOULD BE TEMPERATURES ACROSS OUR SOUTHERN INDIANA COUNTIES WOULD FALL DURING THE AFTERNOON INTO THE MID AND UPPER 40S WITH ALL OF THE KY COUNTIES TEMPERATURES HOLDING STEADY IN THE MID TO UPPER 50S.

CURRENT FORECAST IS GOOD SHAPE RIGHT NOW...BUT WILL NEED TO MAKE SOME MINOR ADJUSTMENTS TO THE TEMP GRIDS TO REFLECT CURRENT RUC TRENDS.

ON THE HYDROLOGICAL SIDE...AT THE PRESENT TIME WE ARE IN GOOD SHAPE. THE LIGHT TO MODERATE RAINS THUS FAR HAVE NOT RESULTED IN EXCESSIVE RUNOFF. HOWEVER...MAIN BULK OF PRECIPITATION ACCUMULATION IS FORECAST TO IMPACT THE REGION LATE TONIGHT AND ON SUNDAY. THEREFORE...CURRENT FLOOD WATCH WILL REMAIN IN EFFECT.

UPDATED FORECAST SUITE WILL BE AVAILABLE BY 1100 AM EST.

-MJ

PREVIOUS DISCUSSION FOLLOWS...

.SHORT TERM (TODAY AND TONIGHT)...

CURRENTLY...DEEP SWRLY FLOW IS DOMINATING ACROSS THE REGION. A COLD FRONT IS QUICKLY APPROACHING FROM THE WEST AND IS PUSHING THROUGH EVV ATTM. LOW-LEVEL COLD AIR IS FILTERING IN BEHIND THE FRONT FASTER THAN MODELS HAD ANTICIPATED. LARGE AMOUNT OF ISENTROPIC LIFT OVER THE COLD AIR HAS LED TO QUITE AN ICING EVENT OVER PORTIONS OF OK INTO MO. LARGE TEMP GRADIENT PRESENT AS WELL...AS PAH WAS AT 60 DEGREES AND CAPE GIRARDEAU AT 39 DEGREES AT 2AM EST.

DESPITE COLD FRONT QUICKLY APPROACHING...A LOW PRESSURE WAVE OVER THE TEXARKANA REGION RIDING NEWD ALONG THE FRONT WILL HELP SLOW THE FRONT`S PROGRESSION...AND WILL BE RESPONSIBLE FOR OUR FIRST WAVE OF POTENTIALLY HEAVY PRECIP...WHICH IS CURRENTLY OVER WRN KY. THIS AREA SHOULD EXPAND AND FILTER INTO OUR CWA THROUGHOUT THE MORNING. MAY EVEN SEE A RUMBLE OF THUNDER OR TWO WITH THIS FIRST BATCH OF RAINFALL GIVEN UPSTREAM TRENDS. WILL ONLY MENTION ISLD THREAT WEST OF I-65 THIS MORNING. AFTER THIS MORNING`S MAIN AREA OF PRECIP...A LULL IN THE PRECIP SHOULD OCCUR THIS AFTERNOON BEFORE ANOTHER LOW PRESSURE WAVE RIDES NEWD ALONG THE FRONT TONIGHT...CAUSING ANOTHER BOUT OF POTENTIALLY HEAVY RAIN.

THOUGH RAIN ONSET IS LATER THAN ANTICIPATED...STILL THINK THE FLOOD WATCH IS WARRANTED THROUGH THE WEEKEND. PWATS ARE OVER AN INCH NOW...AND NAM BUFKIT SOUNDINGS INDICATE NEAR 1.5 INCHES THIS EVENING...WHICH IS SUPPORTED BY THE 4-5 STD DEVIATIONS ABV NORMAL POSED BY THE SHORT-RANGE ENSEMBLES. ALSO...NAM AND GFS INDICATE SOME ELEVATED INSTABILITY WITH LI`S AROUND ZERO TONIGHT...WHICH WILL AID IN OVERALL PRECIP AMOUNTS GIVEN THIS CONVECTION. STILL THINK SOME LOCATIONS COULD SEE 2-3 INCHES OF RAINFALL...WITH ISOLATED LOCATIONS SEEING 4 INCHES OR MORE. HOWEVER...GIVEN THE SLOW ONSET THINK A WIDESPREAD FLOODING EVENT IS NOT LIKELY...THOUGH A MINOR AND MORE ISOLATED FLOODING EVENT IS CERTAINLY POSSIBLE...SO WILL CONTINUE FLOOD WATCH. MAY DOWN PLAY AMOUNTS A WEE BIT BUT THAT IS ALL.

THE FRONT WILL BE CLOSELY ALIGNED WITH THE OHIO RIVER AROUND SUNRISE AND SHOULD BE IN NEARLY THE SAME LOCATION OR JUST SE BY MIDNIGHT TONIGHT. WILL KEEP CATEGORICAL POPS GOING...WITH MENTION OF LOCALLY HEAVY RAINFALL.

FOR AVIATION CONCERNS...HAVE LOW-LEVEL WIND SHEAR IN ALL THE TAF SITES THIS MORNING GIVEN THE STRONG SWRLY JET OF 40-45 KTS OVER THE CWA NOW...EVIDENT FROM AREA VWPS AND SDF ACARS SOUNDINGS. MAY SEE SOME GUSTY WINDS HERE AND THERE...BUT NOTHING OUT OF HAND AS CLOUDY SKIES SHOULD HELP INHIBIT LARGER GUSTS.

TEMPS WILL BE TRICKY TODAY...AND COULD HAVE QUITE THE GRADIENT ACROSS THE CWA...ESPECIALLY BY MIDDAY. TEMPS MAY DROP AND/OR STEADY OUT ACROSS THE NW...WITH CURRENT READINGS IN THE UPPER 50S DROPPING TO THE UPPER 40S AND HOLDING THERE. THE SERN CWA COULD SEE HIGHS A FEW DEGREES WARMER THAN CURRENT READINGS...AND SHOULD STICK AROUND 60 FOR THE MOST PART. OVERNIGHT LOWS WILL NOT BUDGE MUCH AND SHOULD BE JUST A FEW DEGREES COLDER THAN HIGHS TODAY.

AL

.LONG TERM (SUNDAY THROUGH FRIDAY)...

SUNDAY AND MONDAY...

FORECAST CHALLENGE WILL BE PLACEMENT OF THE COLD FRONT AT THE BEGINNING OF THIS PERIOD. LATEST SHORT RANGE MODELS DID NOT INITIALIZE SHALLOW COLD AIR WELL AND FEEL IT WILL BE FURTHER SOUTH THAN MODELS SUGGEST. SURFACE WAVE SHOULD SHIFT THE COLD AIR NORTH SOME DURING THE AFTERNOON SUNDAY AND AT THIS TIME WE WILL KEEP PRECIPITATION ACROSS THE NORTH IN THE FORM OF RAIN. THE AXIS OF HEAVY RAIN SUNDAY AND SUNDAY NIGHT STILL LOOKS TO BE ALONG THE OHIO RIVER WHERE AN INCH TO AN INCH AND A HALF WILL BE POSSIBLE. LIGHTEST AMOUNTS WILL OCCUR ACROSS THE SOUTHEAST PORTION OF THE COUNTY FORECAST AREA. WE WILL HOLD ONTO ISOLATED THUNDERSTORMS SOUTH OF THE OHIO RIVER SUNDAY WHERE BEST DYNAMICS EXIST...ALTHOUGH INSTABILITY WILL BE LACKING.

TEMPERATURES WILL BE A CONCERN AS WELL AS A 10 TO 15 DEGREE GRADIENT WILL BE NOTED ACROSS THE COLD FRONT. HIGHS SUNDAY WILL TOP OUT IN THE LOWER 40S ACROSS SOUTHERN INDIANA WITH UPPER 50S EXPECTED NEAR THE TENNESSEE BORDER.

ONCE THE SURFACE LOW MOVES NORTHEAST OF THE REGION THE MODIFIED ARCTIC AIR WILL ENTER THE FORECAST AREA MONDAY. HIGHEST TEMPERATURES WILL OCCUR DURING THE MORNING. LIGHT SNOW SHOWERS WILL BE POSSIBLE MONDAY BUT NO ACCUMULATION IS EXPECTED.

JA

TUESDAY THROUGH FRIDAY...

NOT MUCH CHANGE IN THE FORECAST THROUGH THIS TIME PERIOD. WITH FRONT CONTINUING TO OUR SOUTH AND HIGH PRESSURE BUILDING IN FROM THE UPPER PLAINS...NORTHERLY WINDS WILL GET THE LAKE-EFFECT SNOW MACHINE GOING TO OUR NORTH. DOWN THIS FAR SOUTH...FEEL THAT SCT FLURRIES WILL BE POSSIBLE DURING THE DAY ON TUESDAY AND WILL LEAVE AS SUCH. BETTER CHC FOR SNOW SHOWERS WOULD EXIST OVER FAR EAST KY IN THE FAVORED UPSLOPE REGIONS. DRY FORECAST IS ANTICIPATED FOR WEDNESDAY THROUGH FRIDAY AS HIGH PRESSURE CONTINUES TO BUILD OVER THE REGION. TEMPERATURES AT THE BEGINNING OF THIS PD WILL BE WELL BELOW NORMAL WITH HIGHS IN THE UPPER 20S TO LOWER 30S AND OVERNIGHT LOWS IN THE UPPER TEENS. SOME MODERATION IN THE TEMPERATURES WILL OCCUR BY THURSDAY AND FRIDAY WITH TEMPERATURES WARMING SLIGHTLY INTO THE MID AND UPPER 30S. GENERALLY STUCK CLOSE TO THE HPC GUIDANCE THROUGH THIS PERIOD.

MJ

&&

.LMK WATCHES/WARNINGS/ADVISORIES... KY...FLOOD WATCH THROUGH LATE SUNDAY NIGHT FOR KYZ023>043-045>049- 053>057-061>067-070>078-081-082.

IN...FLOOD WATCH THROUGH LATE SUNDAY NIGHT FOR INZ076>079-083-084- 089>092.

&&

$$

.SHORT TERM... TONIGHT AND SUNDAY

WILL SIDE MORE WITH THE 12Z NAM-WRF THAN THE 12Z GFS FOR THIS FORECAST PACKAGE. THE THERMAL PROFILES SEEM MORE PLAUSIBLE THAN THE GFS AS SEEN BY MOST CURRENT TAMDAR DATA.

AT 19Z...SFC ANALYSIS DEPICTED A NEARLY STATIONARY FRONTAL BOUNDARY NEAR THE OHIO RIVER. THIS FRONT WILL UNDULATE SOME OVER THE NEXT 24 HOURS AS WAVES OF SFC LOW PRESSURE RIPPLE NE ALONG IT. MEANWHILE...ARCTIC HIGH PRESSURE WAS SPRAWLED FROM ONTARIO WESTWARD INTO THE UPR MS RIVER VLY. COLDER AIR HAS MADE ITS WAY INTO THE NRN THIRD OF THE FCST VIA SFC NE FLOW. THE FORECAST DILEMMA FOR TONIGHT INTO SUNDAY WILL BE HOW FAR SOUTH THE FREEZING LINE WILL MOVE AND HOW THIS WILL AFFECT PCPN TYPE.

FOR TONIGHT...A TANDEM OF UPR LVL S/WVS WILL ROTATE NE INTO THE WRN GREAT LAKES AND OHIO VLY REGION FROM THE SRN PLAINS/LOWER MS RIVER VLY. THESE S/WVS WILL PROVIDE UPR SUPPORT FOR VERTICAL LIFT. IN ADDITION...MODELS INDICATE THAT WARM...MOIST ISENTROPIC LIFT WILL DEVELOP TONIGHT...CONTINUING INTO SUNDAY. THE COMBINATION OF THE LIFT FROM THE S/WVS AND THE LIFT FROM MOIST...WARM AIR ADVECTION WILL CAUSE PCPN TO BREAK OUT FROM W TO EAST OVERNIGHT. WITH TEMPS AT OR BELOW FREEZING ACRS THE NRN TWO THIRDS OF THE FCST AREA AND WITH A WARM TONGUE OF AIR EXPECTED ALOFT...PCPN WILL FALL IN THE FORM OF FREEZING RAIN AND SLEET. ICE ACCUMULATIONS FROM THE FREEZING RAIN WILL BE ON THE LIGHT SIDE OVERNIGHT...MEASURING 0.05 OF AN INCH OR LESS. HOWEVER...ANY ICE WILL BE A HAZARD TO TRAVEL. HENCE...WILL ISSUE WINTER WX AND FREEZING RAIN ADVISORIES FOR TONIGHT STARING AFTER MIDNIGHT. ON SUNDAY...THERE MAY BE A BRIEF LULL IN THE PCPN BY AFTN AS AFOREMENTIONED S/WVS PIVOT OFF TO THE NE. HOWEVER...ANOTHER DISTURBANCE AND STRONGER WAVE OF LOW PRESSURE WILL APCH THE OHIO VALLEY BY EARLY EVENING...SPREADING WIDESPREAD PCPN BACK INTO THE REGION. KEEPING THIS IN MIND...HAVE DECIDED TO KEEP LIKELY POPS FOR THE ENTIRE PERIOD. TEMPERATURES WILL ONLY WARM SLIGHTLY DURING THE DAY...PERHAPS 3 TO 5 DEGREES FROM MORNING LOWS. ANY FREEZING RAIN BY AFTN WILL PROBABLY NOT ACCUMULATE MUCH WITH TEMPS HOVERING IN THE 32 TO 34 DEGREE RANGE. TO KEEP HEADLINES SOMEWHAT SIMPLISTIC WILL EXTEND THE ADVISORY THROUGH THE ENTIRE DAY AS ICING WILL LIKELY OCCUR DURING THE MORNING HOURS (ANOTHER 0.05 OF AN INCH). ALSO...THIS WILL MATCH UP WITH THE LONG TERM FORECASTER/S PLAN TO ISSUE A WINTER STORM WATCH FOR THE SUNDAY NIGHT/MONDAY TIME FRAME DUE TO THE NEXT WEATHER SYSTEM TO AFFECT THE REGION.

&&

.LONG TERM... SUNDAY NIGHT THROUGH SATURDAY

VERY CHALLENGING LONG TERM WITH THE FOCUS CONTINUING TO LIE WITH POTENTIAL MAJOR MIXED PRECIP EVENT AT THE START OF THE PERIOD. WATER VAPOR IMAGERY THIS AFTERNOON SHOWING A WELL DEVELOPED MID/UPPER LEVEL TROUGH AND EMBEDDED CLOSED CIRCULATION OVER THE WESTERN CONUS. A DEEP PLUME OF SUB-TROPICAL MOISTURE EMANATING FROM THE LOW LATITUDES OF THE PACIFIC STRETCHES INTO THE CENTRAL CONUS IN ADVANCE OF THE WESTERN TROUGH WITH PWAT SOME 2-3 STDEV ABOVE NORMAL FOR JAN. THIS WILL SET THE STAGE FOR YET ANOTHER SIGNIFICANT QPF EVENT...ONLY THIS TIME THERE WILL BE A LOW LEVEL ARCTIC AIRMASS ATTEMPTING TO UNDERCUT THE CONTINUED WARM/MOIST SW FLOW ALOFT.

SIMILAR TO MIDNIGHT SHIFT...HAVE LEANED TOWARDS THE STRONGER AND FARTHER NW SOLUTION OF THE NAM OVER THE FLATTER AND SUPPRESSED GFS SOLUTION. THE NAM HAS SUPPORT FROM BOTH THE CANADIAN REGIONAL GEM AND THE UKMET FOR THE PAST SEVERAL RUNS. ON SUNDAY SHORTWAVE ENERGY AND ASSOCIATED HEIGHT FALLS EJECTING OUT OF MEAN WESTERN CONUS TROUGH WILL SPAWN ANOTHER SURFACE WAVE ALONG THE BAROCLINIC BOUNDARY STRETCHING FROM THE SOUTHERN PLAINS INTO THE OHIO VALLEY. BOTH NAM/GFS SHOW RAPIDLY STRENGTHENING UPPER LEVEL JET ACROSS THE GREAT LAKES SUN NGT IN ADVANCE OF TROUGH EJECTION WITH AREA OF STRONG UPPER LEVEL DIVERGENCE DEVELOPING WITHIN THE RIGHT ENTRANCE REGION OVER THE CWA. THE UPPER LEVEL SUPPORT COUPLED WITH LOW LEVEL ISENTROPIC ASCENT/THETA-E ADVECTION SHOULD SUPPORT A BROAD AREA OF LIFT SUN NGT INTO MON AM. GIVEN THE ANOMALOUS HIGH AVAILABLE MOISTURE WITHIN SUB-TROPICAL MOISTURE PLUME...FEEL ALL MODEL GUIDANCE MAY VERY WELL BE UNDER-FORECASTING QPF IN THE COLD SECTOR. SIGNIFICANT QPF OF A HALF INCH OR MORE IS POSSIBLE IN AREAS WHICH WILL BE AT OR BELOW FREEZING AT THE SURFACE...WITH HEAVIER AMOUNTS IN THE FAR SOUTHERN PART OF THE CWA WHERE DEEPER MOISTURE AND WARMER TEMPS ARE FORECAST.

NEXT QUESTION IS PTYPE. AGAIN...FAVORED THE NAM THERMAL PROFILES IN FAVOR OF A STRONGER AND FARTHER NORTH TRACK...WHICH WOULD IMPLY WARMER TEMPS ALOFT. NAM POINT SOUNDINGS FAVORABLE FOR FZRA AND IP ACROSS MUCH OF THE NORTHERN 2/3 OF THE CWA...WITH TENDENCY TOWARDS MORE SLEET FARTHER NORTH WITH A DEEPER NEAR SURFACE COLD LAYER. THE ONLY PORTION OF THE CWA WITH SOUNDINGS SUPPORT SNOW SUN NGT BASED ON CURRENT 12Z NAM RUN WOULD BE THE FAR NW CORNER FROM NEAR MCY TO BEH. FOLLOWING THIS TREND...HAVE REDUCED THE AMOUNT OF SNOW MENTION IN GRIDS AND INCREASED FZRA/IP MENTION. LEFT THE SOUTHERN 1/3 OF THE CWA AS MAINLY RAIN SUN NGT...POSSIBLY SOME FZRA LATE AS TEMPS COOL TO NEAR FREEZING. HAVE HOISTED A WINTER STORM WATCH FOR SUN NGT THROUGH MIDDAY MON FOR ROUGHLY THE NORTHERN 2/3 OF THE CWA FOR A COMBINATION OF FZRA AND SLEET...WITH SOME SNOW IN THE MIX AS WELL IN THE FAR NW. A FLOOD WATCH HAS ALSO BEEN HOISTED FOR THE SAME TIME FRAME ACROSS THE SOUTH FOR A COMBINATION OF POTENTIAL RIVER FLOODING AND ALSO POOR DRAINAGE TYPE FLOODING. STILL SOME UNCERTAINTY WITH EXACT TRACK AND SURFACE TEMPS...BUT IF THE EXPECTED GREATER QPF VERIFIES COULD SEE SIGNIFICANT ICE AND/OR SLEET ACCUMULATION FOR A PORTION OF THE CWA.

ON MONDAY SLOWER/WARMER NAM STILL FAVORS A MIXED BAG IN THE MORNING...THEN AS LOW/MID LEVEL CAA RAMPS UP IN THE AFTERNOON ANY REMAINING PRECIP SHOULD CHANGE TO ALL SNOW FROM NW TO SE. ATTENTION THEN TURNS TO LAKE EFFECT POTENTIAL. FROM LATE MON AFTERNOON THROUGH TUE NW FLOW OF MUCH COLDER AIR ARRIVES. 12Z NAM BUFKIT ANALYSIS SHOWING MODERATE COLLIER INDEX AND FAIRLY WELL ALIGNED NW FLOW WITH A GOOD AMOUNT OF AMBIENT SYNOPTIC SCALE MOISTURE BENEATH AN INVERSION CENTERED AROUND 7K FEET. INSTABILITY PARAMETERS AND PATTERN RECOGNITION POINT TOWARDS A POTENTIALLY DECENT LAKE EFFECT EVENT. THIS IS STILL SEVERAL DAYS OFF...AND WITH FOCUS ON SYNOPTIC EVENT STILL PLENTY OF TIME TO WATCH FUTURE MODEL TRENDS. FOR NOW HAVE INCREASED POPS TO LIKELY SE OF THE LAKE WITH A LARGE AREA OF CHANCE POPS IN AREAS FAVORED BY NW FLOW. LITTLE CHANGE TO REMAINDER OF FORECAST FROM TUE NGT THROUGH SAT.

&&

.AVIATION... COLD FRONTAL BOUNDARY HAS JUST ABOUT STALLED OUT NEAR THE OHIO RIVER THIS AFTERNOON. MOSAIC AND SURROUNDING RADARS INDICATE THAT PCPN HAS ENDED FOR THE MOST PART ACRS THE FCST AREA...AND DRY WX IS EXPECTED THROUGH AT LEAST 06Z SUNDAY. THEN...SVRL WEAK WX DISTURBANCES ALOFT...COMBINED WITH A RETURN TO ISENTROPIC LIFT/WARM MOIST ADVECTION...WILL CAUSE PCPN TO FORM AFTER 06Z...WITH AREAL COVERAGE INCREASING BY 12Z SUNDAY. COLDER AIR HAS FILTERED SOUTHWARD INTO FAR NRN INDIANA...AND TEMPERATURES AT OR BELOW FREEZING ARE EXPECTED AT THE TAF SITES FROM 06Z THROUGH AT LEAST 18Z. THE COLD AIR AT THE SFC IN CONJUNCTION WITH A BULGE OF WARMER AIR ALOFT WILL RESULT IN FZRA AND SLEET. AT THIS POINT...KSBN HAS THE BEST CHC FOR SOME SLEET WHILE KFWA SHOULD ONLY SEE FZRA. CIGS ARE IN THE IFR CATEGORY THIS AFTN...AND THEY WILL DROP INTO THE LIFR CATEGORY OVERNIGHT AFTER THE ONSET OF PCPN. VSBYS TOO WILL DROP INTO THE IFR RANGE IN ASSOCIATION WITH THE PCPN.

&&

.IWX WATCHES/WARNINGS/ADVISORIES... IN...FLOOD WATCH FROM SUNDAY EVENING THROUGH MONDAY AFTERNOON FOR INZ020-INZ022-INZ023-INZ024-INZ025-INZ026-INZ027-INZ032- INZ033-INZ034.

FREEZING RAIN ADVISORY FROM MIDNIGHT EST /11 PM CST/ TONIGHT TO 7 PM EST /6 PM CST/ SUNDAY FOR INZ008-INZ009-INZ013-INZ015- INZ016-INZ017-INZ018.

WINTER STORM WATCH FROM SUNDAY EVENING THROUGH MONDAY AFTERNOON FOR INZ003-INZ004-INZ005-INZ006-INZ007-INZ008-INZ009-INZ012- INZ013-INZ014-INZ015-INZ016-INZ017-INZ018.

WINTER WEATHER ADVISORY FROM MIDNIGHT EST /11 PM CST/ TONIGHT TO 7 PM EST /6 PM CST/ SUNDAY FOR INZ003-INZ004-INZ005-INZ006- INZ007-INZ012-INZ014.

MI...WINTER STORM WATCH FROM SUNDAY EVENING THROUGH MONDAY AFTERNOON FOR MIZ077-MIZ078-MIZ079-MIZ080-MIZ081.

WINTER WEATHER ADVISORY FROM MIDNIGHT TONIGHT TO 7 PM EST SUNDAY FOR MIZ077-MIZ078-MIZ079-MIZ080-MIZ081.

OH...FLOOD WATCH FROM SUNDAY EVENING THROUGH MONDAY AFTERNOON FOR OHZ016-OHZ024-OHZ025.

FREEZING RAIN ADVISORY FROM MIDNIGHT TONIGHT TO 7 PM EST SUNDAY FOR OHZ001-OHZ002-OHZ004-OHZ005-OHZ015.

WINTER STORM WATCH FROM SUNDAY EVENING THROUGH MONDAY AFTERNOON FOR OHZ001-OHZ002-OHZ004-OHZ005-OHZ015.

LM...NONE. &&

$$

SHORT TERM/AVIATION...HICKMAN LONG TERM....HITCHCOCK

.SYNOPSIS...

SIGNIFICANT CONCERNS OVER VALIDITY OF LATEST MODEL RUNS. OF PARTICULAR NOTE IS DEARTH OF OBSERVATIONAL DATA ACROSS SOUTHWESTERN US...ESPECIALLY SOUTHERN NEVADA/NORTHWEST AZ/UT. ACARS DATA AROUND 1200 UTC IS EVEN LACKING. GIVEN MOST PRECIPITATION HAS BEEN DRIVEN BY WEAKER RIPPLES OVER HIGHLY BAROCLINIC LOW LEVELS... CONFIDENCE IS GOING TO BE LOW. ALSO OF NOTE...WATER VAPOR LOOP SUGGEST DECENT AMOUNT OF ENERGY ABOUT TO ROUND THE CLOUD BASE OF LONG WAVE TROUGH WELL OFF GULF OF CA. HOW WELL THIS WILL BE HANDLED IS ALSO SUSPECT. ON THE PLUS SIDE...LATEST RUNS SOMEWHAT SIMILAR TO YESTERDAYS RUNS...WHICH AT LEAST MEANS NO BIG CHANGES FROM PREVIOUS THINKING.

&&

.DISCUSSION...

TONIGHT-SUN:

PLAN TO KEEP HEADLINES GOING...ALTHOUGH MAKING CRITERIA MAY BE MARGINAL. FORCING WILL BE ON THE WANE TONIGHT ONCE CURRENT BATCH OF PRECIPITATION EAST OF I-35 MOVES OUT...WITH LIGHT PRECIPITATION ANTICIPATED FOR REMAINDER OF THE NIGHT. PRECIPITATION TYPE WILL LIKELY BE SOME COMBO OF LIGHT SNOW/LIGHT ICE PELLETS/LIGHT FREEZING DRIZZLE. NEXT SIGNIFICANT SHORTWAVE WILL ENTER SOUTHWEST CORNER OF FORECAST AREA AROUND 1200 UTC...AND SPREAD NE DURING THE DAY. MAIN CONCERN IS AREA WEST OF A LINE FROM KINGMAN TO MCPHERSON...WHERE MARGINALLY DECENT LAPSE RATES AND PERSISTENCE OF LIFT WILL BE MAXIMIZED. 1200 UTC RUNS CONTINUE TO FORECAST A COUPLED UPPER JET SO WILL ALSO BE DECENT UPPER SUPPORT. JUST NOT ENOUGH CONFIDENCE IN LAPSE RATES AND LIFT TO REALLY JUMP ON SNOW AMOUNTS...ESPECIALLY IF FAIR AMOUNT OF THE PRECIPITATION IS SLEET. MINIMUM WILL LIKELY BE AROUND ICT AND AREAS IMMEDIATELY SOUTH. IN SOUTHEAST KS PRECIPITATION WILL START LATE MORNING AND PERSIST INTO THE EVENING. AGAIN SLIGHTLY LONGER PERSISTENCE WILL ADD ACCUMULATION. WITH THERMAL PROFILE NOT EXPECTED TO CHANGE SIGNIFICANTLY...EXPECT A COMBO OF TYPE THERE AS WELL.

SUN NIGHT-MON:

PRECIPITATION WILL MOST LIKELY BE ON THE WANE BY MIDNIGHT. CAVEAT MAY BE IF LAGGING UPPER WAVE DOES SLOW OVERALL PROGRESSION DOWN... PRECIPITATION MAY LINGER INTO MON. GOING CONSENSUS WAS TO NIX PRECIPITATION.

TUE-SAT:

EARLY IN THIS PERIOD MAIN CONCERN WILL BE COLD TEMPERATURES WITH GOOD DIURNAL COOLING FOLLOWED BY MODERATING TEMPERATURES WITH ARCTIC AIRMASS OVER THE AREA. HOW LONG/HOW PRONOUNCED THESE IMPACTS WILL BE WILL BE HIGHLY DEPENDENT ON WHAT OCCURS IN THE NEXT 24-36 HOURS. LATER IN THE PERIOD...GIVEN HIGH LEVEL OF UNCERTAINTY WITH ONGOING PATTERN CHANGE AND ANOTHER PATTERN CHANGE IN THE OFFING FOR LATE IN THE WEEK...OPTED NOT TO INTRO PRECIPITATION CHANCES JUST YET ON DAY 7. AT FACE VALUE...BOTH 0600 UTC GLOBAL FORECAST SYSTEM MODEL/00 UTC EUROPEAN CENTRE FOR MEDIUM RANGE WEATHER FORECASTS MODEL WOULD SUGGEST SOME OVERRUNNING PRECIPITATION NORTH OF FRONTAL BOUNDARY WHICH WOULD MOVE THROUGH THE AREA THU AFTERNOON PER GLOBAL FORECAST SYSTEM MODEL OR LATE FRI AFTERNOON OR EVENING PER EUROPEAN CENTRE FOR MEDIUM RANGE WEATHER FORECASTS MODEL. THE LATTER IS 12 HOUR EARLIER THAN PREVIOUS RUN. DEPTH...TIMING AND ORIENTATION OF LONGWAVE TROUGH OVER WESTERN US ARE STILL UNCERTAIN AS WELL. AT THIS POINT...DOES NOT APPEAR TO BE A MAJOR SURFACE CYCLONE IN THE OFFING WITH THIS UPPER SYSTEM...SO PRECIPITATION WILL BE DEPENDENT ON SUBTLE ORIENTATION OF WINDS AND THERMAL GRADIENT. -HOWERTON

&&

.PRELIMINARY POINT TEMPS/POPS... WICHITA-KICT 11 16 10 19 / 40 100 30 10 HUTCHINSON 10 15 9 18 / 40 100 40 10 NEWTON 10 16 9 18 / 30 100 40 10 ELDORADO 11 17 10 19 / 40 100 40 10 WINFIELD-KWLD 14 19 11 20 / 50 100 20 0 RUSSELL 9 15 7 16 / 40 100 60 10 GREAT BEND 10 15 8 16 / 40 100 50 10 SALINA 10 15 8 17 / 30 100 60 10 MCPHERSON 10 15 9 17 / 30 100 50 10 COFFEYVILLE 17 23 14 22 / 60 100 30 10 CHANUTE 15 21 13 21 / 60 100 30 10 IOLA 14 20 13 20 / 60 100 30 10 PARSONS-KPPF 16 22 14 22 / 60 100 30 10

&&

.ICT WATCHES/WARNINGS/ADVISORIES... WINTER STORM WARNING UNTIL 6 PM CST SUNDAY FOR KSZ032-033- 047>053-067>072-082-083-091>096-098>100.

&&

$$

.SYNOPSIS... WV IMAGERY INDICATED CONFLUENT MID/UPPER LEVEL FLOW FROM THE NRN PLAINS TO THE WRN GREAT LAKES WITH A SRN BRANCH TROF OVER THE SW CONUS AND BROAD CYCLONIC NRN STREAM FLOW THROUGH SRN CANADA. AN UPSTREAM SHRTWV WAS SLIDING SE FROM CNTRL/NRN MANITOBA INTO NW ONTARIO. MID/HIGH CLOUDS WERE ALSO STREAMING INTO THE REGION WITH SW FLOW FROM THE SRN/CNTRL PLAINS. AT THE SFC...A RDG EXTENDED FROM QUEBEC THROUGH UPPER MI TO THE CNTRL PLAINS. AN UPSTREAM ARCTIC COLD FRONT EXTENDED FROM NW ONTARIO TO SRN SASK. LEFTOVER FLURRIES OVER CNTRL AND E UPPER MI WERE QUICKLY DIMINISHING AND MOVING OFFSHORE AS WINDS BACK SWRLY. WITH VERY DRY 900-700 LAYER...PER 19Z TAMDAR SNDGS...NO LIGHT SNOW OR FLURRIES WERE OBSERVED OVER NRN WI DESPITE 10DBZ-20DBZ RADAR RETURNS OVER THE AREA. SHORTWAVE OVR SOUTHWEST WILL BE OF INTEREST LATE SUN INTO MON.

&&

.SHORT TERM (TONIGHT AND SUNDAY) MAIN FCST CONCERNS ARE LES TRENDS.

TONIGHT...EXPECT ENHANCED LOW LVL CONV AND QUICKLY VEERING WINDS AS THE FRONT MOVES THROUGH LK SUPERIOR AND UPPER MI BTWN 06Z-12Z. MOISTURE WITH THIS NRN STREAM SYSTEM IS VERY LIMITED WITH BEST QVECTOR CONV WELL TO THE NORTH...AND MOISTURE INFLOW FROM SW STREAM SHOULD REMAIN MAINLY S OF LK SUPERIOR. SO CONDITIONS WILL BE MARGINAL FOR MORE THEN LIGHT LES. HOWEVER...EXPECCT COVERAGE TO INCREASE LATE TONIGHT WITH THE FRONT MOVING INTO THE KEWEENAW AFT MIDNIGHT AND TOWARD THE NE CWA...MAINLY E OF KP53 AFT 12Z. INVERSION HEIGHTS ARE FCST TO REMAIN IN THE 3K-4K FT RANGE (TEMP NEAR -15C AT THE TOP OF THE INVERSION) WITH ONLY LIMITED CONVECTION DEPTH AND CHANGING WIND DIRECTION...SO ONLY AN INCH OR TWO IS EXPECTED. MID LEVEL CLOUDS THIS EVENING AND LAKE CLOUDS LATER TONIGHT WILL KEEP TEMPS FROM DROPPING OFF QUITE AS MUCH AS PREVIOUS FCST FOR INLAND LOCATIONS.

SUN...AS WINDS VEER MORE NRLY WITH RIDGING INTO NRN ONTARIO BEHIND THE FRONT...LIGHT SNOW SHOWERS WILL SPREAD INTO THE REST OF NORTHERN UPPER MI. AGAIN...WITH ACYC SYNOPTIC FLOW AND 3K FT INVERSION...ONLY LIGHT ACCUMULATIONS EXPECTED...GENERALLY AN INCH OR LESS.

&&

.LONG TERM (SUN NIGHT THROUGH NEXT SAT)...

MAIN CONCERN IN THIS PERIOD IS SNOW AMOUNTS SUN NIGHT THROUGH MON NIGHT.

SHORTWAVE TROUGH FOR SUN NIGHT INTO MON NOW LOOKS LIKE IT WILL LIFT A BIT FARTHER NORTH THAN EARLIER THOUGHT. PRIMARY SFC LOW STILL REMAINS WELL TO THE SOUTH OF UPR MI...TRACKING ACROSS THE NORTHERN OHIO VALLEY. APPEARS THERE WILL BE TWO AREAS OF PCPN. ONE AREA WILL BE ALONG SFC FRONT OVER OHIO VALLEY...WHILE ANOTHER PCPN AREA OF MOSTLY FREEZING RAIN AND SNOW WILL SPREAD ENE ALONG THE MID LEVEL CIRCULATION. ALL GUIDANCE EXCEPT GFS INDICATES AT LEAST SOUTHERN TIER OF CWA WILL BE IMPACTED BY NORTHERN FRINGE OF SNOW FM WI INTO NORTHERN LWR MI. GFS SHARPLY DIFFERENT WITH MORE SHEARED OUT UPR LEVEL WAVE AND NOT AS FAR NORTH OF A PUSH WITH PCPN. FOR NOW...TRIED TO USE A BLEND OF GFS/NAM IDEAS FOR FORECAST. THIS BLENDED IDEA RESULTS IN INCREASE IN POPS IN FAR SCNTRL CWA LATE SUN NIGHT INTO MON WITH SYNOPTIC SNOW. COULD SEE A COUPLE INCHES FM MENOMINEE TO ESCANABA.

CLOSER TO LK SUPERIOR WILL ALREADY HAVE SUFFICIENT INSTABILITY FOR LK EFFECT SNOW IN MOSTLY NNW FLOW BY SUN EVENING. LIKELY POPS LOOK FINE. EXPECT TO SEE SOME INCREASE IN LK EFFECT LATER SUN NIGHT INTO MON AS INVERSION RISES TO AROUND 5KFT AS H85 TEMPS FALL TO -18C OR SO AND PARTIAL DEEP MOISTURE ADVECTS IN FM SOUTH. LOCAL LK EFFECT GUIDANCE SUGGESTS AMOUNTS MEETING ADVY CRITERIA WOULD BE LIKELY SUN NIGHT INTO MON OVER FAR WEST AND NCNTRL CWA WHERE LWR LEVEL WIND DIRECTION OF 350-020 IS FAVORABLE. ONE STUMBLING BLOCK THOUGH...AND A BIG ONE AT THAT...IS THAT IF A SOLN MORE IN LINE WITH NAM IS REALIZED POTENTIAL EXISTS FOR MUCH MORE FAVORABLE SETUP FOR HEAVY LK EFFECT SNOW. KEY IS NAM SHOWING MUCH MORE DEEPER MOISTURE AND AN INVERSION HEIGHT TOWARD H7...WITH THE SAME H85 TEMPS AS GFS AND FOR MOST PART SAME WIND DIRECTION. NAM ALSO INDICATES MUCH MORE CYCLONIC/CONVERGENT LOWER LEVEL FLOW. BASICALLY...IF NAM SOLN VERIFIES ADVY LOOKS FAIRLY CERTAIN AND SOME LOCALIZED WARNING AMOUNTS WOULD BE POSSIBLE.

KIND OF STUCK AT THIS POINT. HARD TO TELL WHICH SOLUTION OR SOLUTION MORE SIMILAR TO IT...WILL VERIFY. USUALLY...TRY TO GO WITH MAJORITY IDEA...BUT WITH GFS SO DIFFERENT AND SOME SUPPORT TO ITS SOLUTION FM ENSEMBLES...TRIED TO GO WITH COMPROMISE SOLUTION FOR SNOW COVERAGE AND AMOUNTS. SINCE CONFIDENCE IS LOW...WILL NOT ISSUE ANY HEADLINES RIGHT NOW EITHER. WILL MENTION THE EVENT IN THE HWO.

LOWER LEVEL FLOW BACKS TO NW ON TUE SO KEPT LK EFFECT OVER NW UPR MI AND FOR AREAS EAST OF MARQUETTE. INVERSION GRADUALLY LOWERS BY TUE NIGHT...SO LK EFFECT INTENSITY SHOULD BE DIMINISHING.

UPR FLOW BRIEFLY BECOMES ZONAL WED WITH LOW PRES PASSING ACROSS NORTHERN MANITOBA AND ONTARIO. WINDS BECOME SW IN LOWER LEVELS WHICH WILL KEEP SNOW SHOWERS ONLY OVER FAR NORTHERN KEWEENAW PENINSULA. SFC TROUGH THEN FOLLOWS INTO UPR LAKES ON THU. UPR TROUGH LIFTING FM PLAINS MAY COMBINE WITH THE SFC BOUNDARY TO BRING A LITTLE LIGHT SNOW THU. MARGINAL DEEPER MOISTURE SO NOTHING MORE THAN LOW CHANCE POPS ATTM. COLDER AIR SPILLS IN FOR FRI SO INCREASED LK EFFECT NEAR LK SUPERIOR IN NW/N FLOW AREAS. LOOSE AGREEMENT ON CLIPPER TYPE SYSTEM FOR SOMETIME NEXT WEEKEND. 00Z/06Z GFS BY FAR THE MOST AGGRESSIVE BUT ECMWF/UKMET/CANADIAN WERE MORE IN LINE WITH PREFERRED LATEST HPC GUIDANCE.

COORD WITH GRB AND DLH...THANKS.

&&

.MQT WATCHES/WARNINGS/ADVISORIES...NONE. &&

$$

SHORT TERM...JLB LONG TERM...JLA