AREA FORECAST DISCUSSION
NWS SAN DIEGO CA
AFDSGX 230 PM PST THU JAN 25 2007
.SYNOPSIS...HIGH PRESSURE ALOFT AND WEAK OFFSHORE FLOW WILL CONTINUE
MOSTLY CLEAR SKIES INTO FRIDAY. COOLER FRIDAY AS ONSHORE FLOW
RETURNS. UPPER LEVEL LOW PRESSURE WILL BRING COOLER DAYS WITH A
RETURN OF COASTAL LOW CLOUDS AND FOG IN THE NIGHTS AND MORNINGS
ALONG WITH VARIABLE HIGH CLOUDINESS THIS WEEKEND AND EARLY NEXT
WEEK.
&&
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
.SHORT TERM (TODAY-SUN)...CLEAR SKIES TODAY. ACARS SOUNDINGS HAD
WEAK ELY WIND THROUGH MOST OF THE COLUMN. WEAK OFFSHORE GRADIENTS
WITH ABOUT -5 MB SAN-TPH AND -2 SAN-IPL.
THE OFFSHORE FLOW WILL STILL CAUSE LOCAL BREEZY CONDITIONS LATE THIS
AFTERNOON AND EARLY EVENING...MAINLY IN AND NEAR THE SAN DIEGO AND
RIVERSIDE COUNTY MOUNTAINS. CONTINUED FAIR BUT A LITTLE COOLER IN
MOST AREAS FRI AS HEIGHTS BEGIN TO LOWER AND ONSHORE FLOW INCREASES.
A WEAK UPPER LOW WILL UNDERCUT THE HIGH AMPLITUDE RIDGE NEAR THE W
COAST THIS WEEKEND. AN EDDY IS EXPECTED TO DEVELOP LATE FRI NIGHT
WITH A RETURN OF MARINE LAYER CLOUDS. LOW CLOUDY MAY START MOVING
ONSHORE FRI AFTERNOON. THERE COULD BE LOCAL DENSE FOG IN THE COASTAL
AREAS AND FAR WRN SAN DIEGO INLAND VALLEYS FRI NIGHT AND SAT
MORNING. THE MARINE LAYER WILL CONTINUE TO DEEPEN INTO SUN BUT BUT
MAY BE BROKEN UP A BIT BY INCREASING HIGH CLOUDINESS. COOLER DAYS.
HIGHER HUMIDITIES AND MORE CLOUDS WILL MODERATE MIN TEMPS W OF THE
MOUNTAINS.
.LONG TERM (MON-THU)...PROGS CONTINUE TO DISAGREE ON THE DETAILS
BUT GENERALLY INDICATE WEAK TROUGHING OVER THE SW EARLY NEXT WEEK.
THIS SHOULD BRING VARIABLE CLOUDINESS WITH A SMALL CHANCE OF LIGHT
PRECIP. HOWEVER...TOO MUCH UNCERTAINTY TO MENTION PRECIP IN THE
FORECAST YET. COOL DAYS BUT STILL MILD AT NIGHT W OF THE MOUNTAINS.
BUILDING HIGH PRESSURE AND OFFSHORE FLOW SHOULD RETURN TOWARD THU OF
NEXT WEEK.
&&
.AVIATION...
WEAK OFFSHORE FLOW WILL CONTINUE VFR CONDITIONS THROUGH FRIDAY
MORNING WITH A CLEAR SKY AND UNRESTRICTED VISIBILITIES. SOME WINDS
IN SOUTHERN SAN DIEGO COUNTY MAY CAUSE LOCAL TURBULENCE AND LLWS
THIS AFTERNOON. WEAK ONSHORE FLOW IS EXPECTED TO RETURN TO THE COAST
FRIDAY AFTERNOON WHICH COULD BRING SOME STRATUS/FOG BACK TO THE
COASTAL AIRPORTS FRIDAY EVE.
&&
.SGX WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
PUBLIC...DVA
AVIATION...MM
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
AFDLOT 930 AM CST THU JAN 25 2007
.MORNING DISCUSSION...
930 AM CST
INHERITED FORECAST SEEMS TO HAVE THE LAKE EFFECT SNOW SITUATION WELL
IN HAND. EXPECTING A FEW MORE HOURS OF LAKE EFFECT SNOW SHOWERS
ACROSS NORTHEAST PORTER COUNTY BEFORE SNOW TAPERS TO FLURRIES.
REPORTS ARE TOUGH TO COME BY THIS MORNING ACROSS NORTHEAST PORTER
COUNTY...BUT DID RECEIVE A REPORT OF 1 TO 2 INCHES OF SNOW IN
WANATAH JUST EAST OF THE PORTER COUNTY LINE. 1 TO 3 INCHES STILL
DOES SEEM TO BE IN ORDER IN TERMS OF SNOWFALL ACCUMULATIONS ACROSS
NORTHEAST PORTER COUNTY WITH SOME LOCALIZED HIGHER AMOUNTS CLOSER TO
4 INCHES POSSIBLE ACROSS THE EXTREME NORTHEAST PART OF THE COUNTY.
OTHERWISE MOSTLY SUNNY SKIES PERSIST ACROSS REMAINDER OF THE
FORECAST AREA EXCEPT IN NORTHWEST ILLINOIS WHERE LOW CLOUDS ARE
LINGERING CLOSER TO THE LOW LEVEL RIDGE AXIS. AT THIS
TIME...EXPECTING STRENGTHENING SUBSIDENCE SHOULD PREVENT SUBSTANTIAL
CLOUD COVER ACROSS MUCH OF THE FORECAST AREA TODAY...SO WILL
MAINTAIN PARTLY CLOUDY CONDITIONS THROUGH THE AFTERNOON. TEMPS/WINDS
ALSO APPEAR TO BE ON TRACK.
MARSILI
&&
.DISCUSSION MORNING GRIDS/ZONES...
445 AM CST
NO SIGNIFICANT CHANGES NECESSARY TO GOING FORECAST...AND NO MAJOR WX
CONCERNS OVER THE NEXT SEVERAL DAYS.
SHORT WAVE TROUGH CROSSED THROUGH THE REGION OVERNIGHT AND IS NOW
MOVING INTO THE LOWER LAKES AND UPPER OH VALLEY WITH SUBSIDENCE AND
DRYING IN ITS WAKE CLEARING OUT CLOUDS FROM MOST OF WI AND IL. WITH
CORE OF COLD AIR OVER THE ONTARIO/QUEBEC BORDER THE DEPTH OF
REINFORCING COLD AIR ACROSS THE WESTERN GREAT LAKES IS RATHER
SHALLOW. LAKE EFFECT SHOW QUICKLY DEVELOPED EARLIER THIS MORNING
WITH THE WESTERN EDGE CLIPPING EASTERN PORTER COUNTY AS THE BOUNDARY
LAYER FLOW HAS VEERED TO NNW. FORECAST TEMPERATURE PROFILE OVER
SOUTHERN LAKE MI INDICATES TOPS OF LAKE EFFECT CLOUDS TO REACH TO
AROUND 7K FT ALLOWING MODERATELY VIGOROUS SNOW SHOWERS. WINDS
ALREADY BACK TO NW BY 18Z SHIFTING THE LAKE EFFECT OUT OF THE FA
LIMITING THE TIME OF POSSIBLE ACCUMULATION. FAR NE PORTER MAY SEE
1-3 INCHES THIS MORNING.
SURFACE RIDGE CROSSES AREA THIS EVENING WITH INCREASING SW LOW LEVEL
FLOW OVERNIGHT. THIS IN RESPONSE TO LOW PRESSURE DEEPENING AND
MOVING ACROSS SASKATCHEWAN TO MANITOBA BY FRI MORNING AS STRONG
SHORT WAVE MOVES SE FROM NORTHERN B.C. WAA AND UVV SPREAD E INTO THE
NORTHERN LAKES OVERNIGHT AND INTO THE CENTRAL LAKES DURING THE DAY
FRI. SNOW IN THE ZONE OF STRONG ISENTROPIC LIFT WILL PASS BY TO THE
N AND NE OF THE LOCAL AREA. AS THE SHORT WAVE CONTINUES ESE TO LAKE
SUPERIOR FRI NIGHT THE ASSOCIATED SURFACE LOW MOVE INTO THE CENTRAL
LAKES AND A COLD FRONT PUSHES SE INTO THE FA DELIVERING MORE COLD
AIR DEEPER ACROSS THE PLAINS AND MIDWEST. DEW POINTS TO CLIMB IN THE
MID 20S ON THE SW FLOW AHEAD OF THE COLD FRONT AND WITH FROPA FRI
NIGHT STRONG SHALLOW CAA SETS IN AND A PERIOD OF LIGHT FREEZING
DRIZZLE POSSIBLE POST FROPA.
A COUPLE MORE WAVES TO DROP INTO THE UPPER TROUGH SAT AND SUN
DEEPENING IT ACROSS THE OH VALLEY. THESE IMPULSES TO GENERATE ONLY
SOME FLURRIES EXCEPT POTENTIAL FOR LAKE EFFECT TO MOVE BACK INTO FAR
NW FOR SUN DEPENDING ON HOW MUCH THE LOW LEVEL FLOW VEERS. WITH COLD
AIR AND RELATIVELY WARM LAKE WATERS A LOW PRESSURE TROUGH TENDS TO
LAY OUT E-W ACROSS THE UPPER GREAT LAKES AND THIS MAY TEND TO KEEP
SURFACE WINDS ON SOUTHERN LAKE MI FROM THE NW VS NNW.
WITH THE UPPER TROUGH AXIS OVER THE GREAT LAKES SUN INTO MID WEEK
TEMPS WILL BE BELOW NORMAL AFTER RUNNING NEAR NORMAL FRI AND SAT.
TRS
&&
.AVIATION...
616 AM CST
SOME VFR TO HIGH MVFR CLOUDS MAY MOVE INTO NORTH CENTRAL ILLINOIS
THIS MORNING. A BAND OF CLOUDS WAS SEEN OVER WESTERN WISCONSIN THIS
MORNING AT 11 AND 12 UTC. THE WIND FLOW IS FROM THE NORTHWEST AS
SEEN ON THE PROFILER 850 MB WIND. WILL ADD A BROKEN VFR LAYER OVER
RFD IN THIS MORNINGS FORECAST. THE ACARS SOUNDING SHOW A SHALLOW
INVERSION AROUND 1330 FT AT RFD 848 UTC. THE WIND ABOVE THIS
INVERSION INCREASES TO AROUND 30 KNOTS FROM THE NORTH. THE FORECAST
WIND IS AROUND 9 KNOTS THIS MORNING BUT MAY INCREASE TO 10 TO 15
KNOTS LATER TODAY. THE SNOW COVER MAY KEEP THE AIR NEAR THE GROUND
COLD ENOUGH TO MAINTAIN THE INVERSION. WE EXPECT THE WIND TO BECOME
SOUTHWEST BY 04 UTC FRIDAY. THE SURFACE HIGH PRESSURE RIDGE WILL
PASS OVER NORTHEAST ILLINOIS AND NORTHWEST INDIANA EARLY TONIGHT.
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
.IL...NONE.
.IN...NONE.
.LM...SMALL CRAFT ADV IN EFFECT THROUGH THIS AFTEROON.
&&
$$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
AFDLOT 616 AM CST THU JAN 25 2007
.DISCUSSION MORNING GRIDS/ZONES...
445 AM CST
NO SIGNIFICANT CHANGES NECESSARY TO GOING FORECAST...AND NO MAJOR WX
CONCERNS OVER THE NEXT SEVERAL DAYS.
SHORT WAVE TROUGH CROSSED THROUGH THE REGION OVERNIGHT AND IS NOW
MOVING INTO THE LOWER LAKES AND UPPER OH VALLEY WITH SUBSIDENCE AND
DRYING IN ITS WAKE CLEARING OUT CLOUDS FROM MOST OF WI AND IL. WITH
CORE OF COLD AIR OVER THE ONTARIO/QUEBEC BORDER THE DEPTH OF
REINFORCING COLD AIR ACROSS THE WESTERN GREAT LAKES IS RATHER
SHALLOW. LAKE EFFECT SHOW QUICKLY DEVELOPED EARLIER THIS MORNING
WITH THE WESTERN EDGE CLIPPING EASTERN PORTER COUNTY AS THE BOUNDARY
LAYER FLOW HAS VEERED TO NNW. FORECAST TEMPERATURE PROFILE OVER
SOUTHERN LAKE MI INDICATES TOPS OF LAKE EFFECT CLOUDS TO REACH TO
AROUND 7K FT ALLOWING MODERATELY VIGEROUS SNOW SHOWERS. WINDS
ALREADY BACK TO NW BY 18Z SHIFTING THE LAKE EFFECT OUT OF THE FA
LIMITING THE TIME OF POSSIBLE ACCUMULATION. FAR NE PORTER MAY SEE
1-3 INCHES THIS MORNING.
SURFACE RIDGE CROSSES AREA THIS EVENING WITH INCREASING SW LOW LEVEL
FLOW OVERNIGHT. THIS IN RESPONSE TO LOW PRESSURE DEEPENING AND
MOVING ACROSS SASKATCHEWAN TO MANITOBA BY FRI MORNING AS STRONG
SHORT WAVE MOVES SE FROM NORTHERN B.C. WAA AND UVV SPREAD E INTO THE
NORTHERN LAKES OVERNIGHT AND INTO THE CENTRAL LAKES DURING THE DAY
FRI. SNOW IN THE ZONE OF STRONG ISENTROPIC LIFT WILL PASS BY TO THE
N AND NE OF THE LOCAL AREA. AS THE SHORT WAVE CONTINUES ESE TO LAKE
SUPERIOR FRI NIGHT THE ASSOCIATED SURFACE LOW MOVE INTO THE CENTRAL
LAKES AND A COLD FRONT PUSHES SE INTO THE FA DELIVERING MORE COLD
AIR DEEPER ACROSS THE PLAINS AND MIDWEST. DEW POINTS TO CLIMB IN THE
MID 20S ON THE SW FLOW AHEAD OF THE COLD FRONT AND WITH FROPA FRI
NIGHT STRONG SHALLOW CAA SETS IN AND A PERIOD OF LIGHT FREEZING
DRIZZLE POSSIBLE POST FROPA.
A COUPLE MORE WAVES TO DROP INTO THE UPPER TROUGH SAT AND SUN
DEEPENING IT ACROSS THE OH VALLEY. THESE IMPULSES TO GENERATE ONLY
SOME FLURRIES EXCEPT POTENTIAL FOR LAKE EFFECT TO MOVE BACK INTO FAR
NW FOR SUN DEPENDING ON HOW MUCH THE LOW LEVEL FLOW VEERS. WITH COLD
AIR AND RELATIVELY WARM LAKE WATERS A LOW PRESSURE TROUGH TENDS TO
LAY OUT E-W ACROSS THE UPPER GREAT LAKES AND THIS MAY TEND TO KEEP
SURFACE WINDS ON SOUTHERN LAKE MI FROM THE NW VS NNW.
WITH THE UPPER TROUGH AXIS OVER THE GREAT LAKES SUN INTO MID WEEK
TEMPS WILL BE BLEOW NORMAL AFTER RUNNING NEAR NORMAL FRI AND SAT.
TRS
&&
.AVIATION...
616 AM CST
SOME VFR TO HIGH MVFR CLOUDS MAY MOVE INTO NORTH CENTRAL ILLINOIS
THIS MORNING. A BAND OF CLOUDS WAS SEEN OVER WESTERN WISCONSIN THIS
MORNING AT 11 AND 12 UTC. THE WIND FLOW IS FROM THE NORTHWEST AS
SEEN ON THE PROFILER 850 MB WIND. WILL ADD A BROKEN VFR LAYER OVER
RFD IN THIS MORNINGS FORECAST. THE ACARS SOUNDING SHOW A SHALLOW
INVERSION AROUND 1330 FT AT RFD 848 UTC. THE WIND ABOVE THIS
INVERSION INCREASES TO AROUND 30 KNOTS FROM THE NORTH. THE FORECAST
WIND IS AROUND 9 KNOTS THIS MORNING BUT MAY INCREASE TO 10 TO 15
KNOTS LATER TODAY. THE SNOW COVER MAY KEEP THE AIR NEAR THE GROUND
COLD ENOUGH TO MAINTAIN THE INVERSION. WE EXPECT THE WIND TO BECOME
SOUTHWEST BY 04 UTC FRIDAY. THE SURFACE HIGH PRESSURE RIDGE WILL
PASS OVER NORTHEAST ILLINOIS AND NORTHWEST INDIANA EARLY TONIGHT.
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
.IL...NONE.
.IN...NONE.
.LM...SMALL CRAFT ADV IN EFFECT FROM THIS EVENING THROUGH THURSDAY
AFTERNOON.
&&
$$
AREA FORECAST DISCUSSION
NWS LOUISVILLE KY
AFDLMK 1230 AM EST THU JAN 25 2007
.AVIATION (06Z TAFS)...
MAIN CONCERN OVER THE NEXT SEVERAL HOURS IS AREA OF SNOW DROPPING
SOUTH OUT OF INDIANA. THIS SNOW WILL AFFECT SDF AND LEX TERMINALS
THE MOST...PRIMARILY BETWEEN 09Z AND 16Z. BWG WILL CATCH A FEW
FLURRIES FROM IT BUT THAT SHOULD BE ABOUT IT THERE. CEILINGS AND
VISIBILITIES WILL GO MVFR...AND DURING THE HEIGHT OF THE SNOW
SHOWERS AT SDF AND LEX WILL LIKELY DROP SLIGHTLY BELOW 2000 FEET.
AS THE AXIS OF THE UPPER TROF RESPONSIBLE FOR THESE SNOW SHOWERS
MOVES TO OUR EAST THE SNOW SHOULD EXIT AS WELL...BY MIDMORNING. WITH
HIGH PRESSURE NOSING IN FROM THE WEST SKIES WILL MOSTLY CLEAR BY
LATE MORNING AT SDF AND BWG. WILL KEEP THE CLOUDS IN AT LEX LONGER
AS THE MOISTURE TAKES A BIT MORE TIME TO SCOUR OUT OF THAT AREA IN
THESE NORTHWEST FLOW SITUATIONS PLUS SOME CLOUD ENHANCEMENT COMING
OFF LAKE MICHIGAN.
BY LATE AFTERNOON CLOUDS SHOULD BE GONE AND CLEAR SKIES WILL
CONTINUE INTO THE EVENING.
WINDS COULD GET A BIT GUSTY OUT OF THE NORTH TODAY AS THE GRADIENT
TIGHTENS.
13
&&
.EVENING UPDATE...
UPDATED EVENING FORECAST TO REFLECT CLOUD TRENDS. ALBERTA CLIPPER
CURRENTLY SEEN ON WATER VAPOR SATELLITE CURRENTLY OVER WISCONSIN
WILL DIVE SOUTHWARD AND MOVE ACROSS EASTERN KENTUCKY EARLY TOMORROW.
MOISTURE IS LACKING AND AIR REMAINS UNSATURATED ABOVE 800 MB
ACCORDING TO NAM CROSS SECTIONS. HOWEVER...STRONG COLD AIR ADVECTION
WILL BEGIN IN EARNEST EARLY TOMORROW. AS LOW LEVEL LAPSE RATES
STEEPEN...SCATTERED SNOW SHOWERS STILL EXPECTED TO DEVELOP ACROSS
EASTERN INDIANA...AND MOVE ACROSS OUR NORTHEASTERN COUNTIES. HAVE
PUSHED BACK THE POSSIBLE ONSET OF SNOW SHOWERS TO THE PRE-DAWN HOURS
TO CORRESPOND WITH COLDER AIR`S ARRIVAL. SOME LIGHT LOCALIZED
ACCUMULATIONS STILL POSSIBLE ACROSS THE BLUEGRASS REGION UNDER THE
HEAVIER SHOWERS. TEMPERATURES WILL NOT RISE MUCH TOMORROW...AS
BLUSTERY NORTHWEST WINDS WILL DEVELOP BY LATE MORNING AS COLDER AIR
ARRIVES. JSD
.SHORT TERM (TONIGHT-THURSDAY)...
DUE TO CLIPPER SYSTEM...NE SECTIONS OF THE LMK CWA SAW MEASURABLE
SNOW EARLY THIS MORNING...WITH AMOUNTS RANGING FROM A FEW TENTHS TO
NEARLY 1.5 INCHES. NUMEROUS TRAFFIC ACCIDENTS OCCURRED DURING THE
MORNING COMMUTE. TEMPERATURES HAVE RISEN ABOVE FREEZING...MELTING
NEARLY ALL THE SNOW PER WEBCAMS. POWERFUL JET STREAK OVERHEAD
TODAY...EARLIER 737 AIRCRAFT OBSERVATION AT FL380 NEAR SDF
INDICATED A 183KT WESTERLY WIND (AND MODERATE TURBULENCE).
FOCUS FOR THIS PERIOD IS ON YET ANOTHER CLIPPER SYSTEM FCST TO ROLL
THOUGH THE DISTRICT THURSDAY. CURRENTLY FEATURE IS POSITIONED OVER
WRN SECTIONS OF ONTARIO...AND IS FCST TO DROP QUICKLY FROM SRN
INDIANA AT 12Z/THU INTO ERN KY BY 18Z/THU. AHEAD OF THIS UPPER WAVE
FCST SOUNDINGS FROM GFS/NAM SHOW STEEPENING LAPSE RATES LATE TONIGHT
AND THURSDAY WITH SATURATION INTO THE CRITICAL ICE CRYSTAL
GENERATION LAYERS OVER NE 1/3 OF THE CWA...THOUGH GFS IS LESS
AGGRESSIVE WITH SATURATION AS COMPARED TO THE NAM. SCT SHSN ARE
EXPECTED OVER THE NRN/ERN ZONES FROM ROUGHLY 8Z TONIGHT THROUGH 15Z
THURSDAY MORNING.
WE WILL GO WITH 30-40% POPS FOR THIS AREA...LESSER VALUES OVER
REMAINDER OF CWA INCLUDING MOST OF SRN KY...WHERE ONLY FLURRIES WILL
BE MENTIONED. BUFKIT DIAGNOSTICS FROM WETTER NAM PRODUCE AROUND 0.5
INCH OF SNOWFALL FROM MADISON INDIANA SE INTO THE FFT/LEX AREAS...
WITH AROUND 0.25 INCH AT SDF. THESE VALUES SEEM REASONABLE...THOUGH
THEY WILL BE LOCALIZED DEPENDING ON EXACTLY WHERE SNOW SHOWERS
DEVELOP. AN SPS WILL BE ISSUED FOR OUR FAR NE COUNTIES HIGHLIGHTING
POTENTIAL FOR MORE SNOW...AND SIMILAR IN NATURE TO THIS MORNINGS
ACTIVITY...IT HAS THE POTENTIAL TO AFFECT THE MORNING DRIVE TOMORROW.
IN THE MEANTIME...CURRENT AREA OF LOW CLOUDS IS EXPECTED TO
DISSIPATE AND/OR SLIDE SE SUCH THAT SKIES WILL GO PARTLY CLOUDY OR
MOSTLY CLEAR OVER MUCH OF THE CWA FROM LATE AFTN INTO EARLY EVENING.
THEN TOWARD 6Z LOW LEVEL RH FIELDS DEPICT CLOUDS RAPIDLY INCREASING
INTO THE OVERNIGHT HOURS. REGARDING TEMPERATURES...HAVE FOLLOWED
LATEST RUC PROJECTIONS FOR TONIGHT AND TOMORROW GIVEN IT`S RECENT
GOOD PERFORMANCE. THIS YIELDS VERY SLOWLY FALLING TEMPS TONIGHT INTO
THE UPPER 20S/LOWER 30S...WITH NEAR STEADY READINGS THURSDAY.
STEEPENING LAPSE RATES WILL PROMOTE GUSTY WINDS THURSDAY...BUFKIT
SUGGESTING GUSTS TO 20KTS OR SO POSSIBLE AND HAVE FOLLOWED THIS.
CS
.LONG TERM (THURSDAY NIGHT-WEDNESDAY)...
THURSDAY NIGHT AND FRIDAY...
COLD AIR ADVECTION WILL IN IN PLACE AT THE BEGINNING OF THIS
FORECAST PERIOD WITH THE 8H ISOTHERM AT 00Z FRIDAY SOUTH OF THE
FORECAST AREA. THIS IS IN THE WAKE OF A CLIPPER MOVING TO OUR
SOUTHEAST. THIS CAA WILL BE SHORT LIVED AS THE NEXT CLIPPER SYSTEM
BEGINS TO DROP SOUTH OUT OF CENTRAL CANADA. LOW LEVEL WINDS WILL
BACK AND INCREASE FROM THE WEST FRIDAY AND A WARM FRONT WILL MOVE
THROUGH THE AREA. BY 00Z SATURDAY H8 TEMPS WILL HAVE WARMED TO THE
FREEZING MARK. SO AFTER A CLEAR AND COLD THURSDAY NIGHT...FRIDAY
WILL BE BREEZY AND WARMER.
TEMPERATURES FRIDAY MORNING WILL START OUT IN THE LOWER 20S BUT WITH
THE WARMING READINGS WILL RISE INTO THE LOWER AND MID 40S BY
AFTERNOON. SOUTHWEST WINDS FRIDAY NIGHT WILL KEEP TEMPERATURES IN
THE 30S WITH INCREASING CLOUDS.
SATURDAY THROUGH WEDNESDAY...
A GREAT LAKES AND OHIO VALLEY UPPER LEVEL TROUGH WILL REMAIN IN
PLACE THROUGH THIS FORECAST PERIOD. EXTENDED MODELS ARE IN AGREEMENT
ON BRINGING SEVERAL DISTURBANCES THROUGH THE FLOW WHICH WILL BRING
SOME ADDITIONAL LIGHT RAIN OR SNOW TO THE AREA AS WELL AS
REINFORCING COLD AIR.
THE FIRST WAVE WILL SHARPEN UP SATURDAY AND SLOWLY MOVE ACROSS THE
REGION SUNDAY. WITH BACKING LOW LEVEL WINDS AHEAD OF THE DEEPENING
TROUGH ENOUGH WARM AIR WILL FILTER INTO THE REGION TO PRODUCE LIGHT
RAIN SATURDAY. COLDER AIR WILL OVERSPREAD THE LOWER OHIO VALLEY
SATURDAY NIGHT SO ANY ADDITIONAL PRECIPITATION WILL BE IN THE FORM
OF SNOW. WE WILL KEEP POPS IN THE LOW CHANCE CATEGORY BUT IF WE SEE
PERSISTENCE IN THIS CLIPPER SYSTEM POPS WILL NEED TO BE RAISED
ESPECIALLY OVER THE NORTHEAST PORTION OF THE FORECAST AREA.
A SECOND WAVE WILL DIG INTO THE REGION TUESDAY WITH SOME VARIATION
IN THE MODELS ON THE LOCATION AND STRENGTH. FOR NOW WE WILL FOLLOW
THE GFS AND KEEP THE FORECAST AREA DRY.
THE INITIAL SHOT OF COLD AIR SATURDAY NIGHT WILL DROP TEMPERATURES
INTO THE 20S AND LOW 30S SUNDAY AND INTO THE TEENS AND 20S MONDAY
WITH A SLIGHT WARM UP TUESDAY. COLDER TEMPERATURES WILL BE NOTED
AGAIN WEDNESDAY AS THE SECOND CLIPPER MOVES TO THE SOUTHEAST.
--JA
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
KY...NONE.
IN...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS BALTIMORE MD/WASHINGTON DC
AFDLWX 830 PM EST FRI JAN 26 2007
FCST IN GOOD SHAPE. 5-6K BASED CLD DECK EXITING REGION FROM THE SW.
SKIES ARE MCLR ATTM ACRS THE SWRN 1/3RD OF AREA. WILL FRESHEN UP
WORDING FOR THOSE ZONES...AND REMOVE FIRST PD EVENING REFERENCES ALL
ZONES.
TEMPS A SLIGHT TRICK. DWPTS WOULD SUGGEST LOWER VALUES FOR
TNGT...BUT GFS SHOWS DECENT GRADIENT IN PLACE OVERNIGHT IN SPITE OF
LOW MOS SPEEDS. WILL LEAVE MINS WHERE THEY ARE.
WINDS BLO SCA CRITERIA AREAWIDE ON THE MARINE SIDE.
RDH
&&
PREV DISC...
------------------------------------------------------------
.SHORT TERM /TONIGHT THROUGH SATURDAY/...
WATER VAPOR LOOP SHOWS A TROUGH MOVING INTO THE ATLANTIC. THE NEXT
NORTHERN STREAM WAVE IS DIVING SOUTHEAST INTO THE LAKE WINNIPEG
REGION OF SOUTH CENTRAL CANADA...WHILE AN UPPER LOW BEGINS TO LIFT
NORTHEAST INTO THE FOUR CORNERS REGION OF THE SOUTHWEST CONUS. ACARS
400-250MB WIND OBSERVATIONS REVEAL A 100-140KT NORTHWESTERLY JET
DIVES SOUTHEAST FROM THE CENTRAL GREAT LAKES THROUGH THE MID
ATLANTIC. 12Z SURFACE ANALYSIS PLACED A WARM FRONTAL BOUNDARY FROM A
1000MB CYCLONE NORTH OF MINNESOTA SOUTHEAST ACROSS THE GREAT LAKES
WHERE IT BECAME STATIONARY...AND FURTHER EAST THROUGH LOWER NEW
ENGLAND WHERE IT REMAINED A COLD FRONT. A TROUGH WAS LOCATED IN THE
LEE OF THE APPALACHIANS...WITH A 1026MB ANTICYCLONE ACROSS THE GULF
STATES.
ACARS OBSERVATIONS DURING THE DAY INDICATE THE NORTHWESTERLY UPPER
LEVEL JET CONTINUES TO LIFT NORTHEAST INTO NEW ENGLAND AS RIDGING
OCCURS ALOFT. THIS WILL SUPPORT WARM ADVECTION MID LEVEL CLOUDS TO
ADVECT IN ON THE JET AXIS THROUGH THE EVENING. LINEAR EXTRAPOLATION
AND MODEL GUIDANCE SUGGEST THESE CLOUDS WILL LIFT NORTHEAST OF THE
FORECAST AREA WITH THE JET AXIS BY MIDNIGHT. WITH DRY DEW
POINTS...CLEARING SKIES AND DECOUPLING...HAVE UNDERCUT MOS GUIDANCE
FOR LOW TEMPERATURES...ESPECIALLY ACROSS CENTRAL VIRGINIA WHERE
CLEARING OCCURS FIRST. WARM ADVECTION ALOFT SHOULD SUPPORT MID 20S
ACROSS THE HIGHER TERRAIN ABOVE 2500FT (WHERE TEMPERATURES WILL BE
STEADY OR SLOWLY WARM).
CURRENTLY PLENTY OF CLEAR SKIES TO THE SOUTH AND WEST...AND AM
EXPECTING A SUNNY START TO SATURDAY. AS THE UPPER LOW CONTINUES TO
WEAKEN AND THEN LIFT THROUGH THE PLAINS TOMORROW...ANTICIPATE
CLOUDINESS BEING ADVECTED DOWNSTREAM. IN ADDITION...FORCING WILL BE
INCREASING ACROSS THE OHIO VALLEY DURING THE AFTERNOON IN ADVANCE OF
THE NORTHERN STREAM SYSTEM TRAVERSING THE GREAT LAKES. WITH
CONTINUED WARM ADVECTION...TEMPERATURES WILL REBOUND INTO THE 40S
AND 50S.
&&
.LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/...
FAIRLY ACTIVE MID LEVELS AT THE BEGINNING OF THE EXTENDED PERIOD.
SEVERAL SHORTWAVES MOVING EAST IN THE FLOW. 1) A SOUTHERN STREAM
SHORTWAVE PROGGED TO MOVE JUST SOUTH OF THE CWFA. 2) A SHORTWAVE
OVER THE SOUTHERN GREAT LAKES THAT IS EXPECTED TO SHEAR OUT AS IS
MOVES NORTHEAST. 3) LASTLY...A STRONG SHORTWAVE THAT WILL DIG A
TROUGH OVER THE MID MISSISSIPPI VALLEY THAT IS EXPECTED TO CROSS THE
CWFA SUNDAY NIGHT. EVEN AFTER SUNDAY NIGHT...THE FAST ZONAL FLOW
WILL BRING SEVERAL HARD TO TIME SHORTWAVES EAST IN THE FLOW THROUGH
TUESDAY. BY WEDNESDAY A SECOND LONGWAVE TROUGH WILL BEGIN TO MOVE
OVER THE CWFA...FOLLOWED BY A THIRD TOWARDS THE END OF THE WEEK.
BY 00Z SUNDAY...A FRONTAL BOUNDARY IS MOVING EAST ACROSS THE CWFA.
THIS FEATURE SHOULD BE EAST OF THE ARE BY EARLY SUNDAY. THE GFS
PAINTS QPF ACROSS MOST OF THE CWFA...AND WILL BE COLD ENOUGH FOR ALL
SNOW. HAVE RAISED THE POPS AROUND 10 PERCENT ACROSS THE BOARD.
UPSLOPE SNOW SHOWERS ARE ONCE AGAIN EXPECTED ACROSS THE WESTERN
RIDGES THROUGH MOST OF SUNDAY...AND WILL BE AIDED BY THE STRONG
SHORTWAVE ENERGY. AS SECOND BOUNDARY IS EXPECTED MID-WEEK WITH MOST
OF THE PRECIP CONFINED TO THE WESTERN HALF OF THE CWFA. GFS HAS A
COASTAL LOW MOVING UP THE EASTERN SEABOARD LATE-WEEK.
&&
.AVIATION...
RIDGING ALOFT WILL SHUNT MID LEVEL CLOUDS TO THE NORTHEAST AS WINDS
DECOUPLE OVERNIGHT.
&&
.MARINE...
THE SMALL CRAFT ADVISORY CONTINUES ACROSS THE MARYLAND CHESAPEAKE
BAY. WITH GRADIENT RELAXING FROM THE WEST...WINDS ACROSS THE POTOMAC
HAVE LOST THEIR GUSTINESS. THIS TREND WILL CONTINUE ACROSS THE BAY
DURING THE LATE AFTERNOON.
12Z ETA/MAV MOS AT THOMAS POINT INDICATE SUSTAINED WINDS DIMINISH
DURING THE EVENING...BEFORE INCREASING TO ABOUT 10KT WITH A
SOUTHERLY WIND COMPONENT. 12Z NAM/GFS PROXIMITY BUFKIT FORECAST
SOUNDINGS ADDITIONAL MOMENTUM TRANSFER OF UP TO 20KTS SATURDAY FROM
MID MORNING ONWARD.
SMALL CRAFT CONDITIONS ARE LIKELY ON THE WATERS SUNDAY NIGHT AND
MONDAY BEHIND A FROPA.
&&
WATER LEVELS ARE CURRENTLY A FOOT BELOW ASTRONOMIC PREDICTIONS. THE
LUNAR CYCLE IS WAXING (60% FULL). BLOWOUT CONDITIONS OCCURRED LAST
NIGHT.
THE CHESAPEAKE BAY OPERATIONAL FORECAST SYSTEM AND THE NOAA
EXTRATROPICAL STORM SURGE MODEL BOTH SUGGEST TIDAL DEPARTURES
RECOVER TO OR SLIGHTLY ABOVE ASTRONOMIC PERDITIONS THIS EVENING AND
TONIGHT.
&&
.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 PM EST THIS AFTERNOON FOR
ANZ530>534.
SMALL CRAFT ADVISORY FROM 10 AM TO 5 PM EST SATURDAY FOR
ANZ530>537.
&&
$$
SHORT TERM/AVIATION/MARINE/TIDES...ROGOWSKI
LONG TERM/MARINE...LISTEMAA
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
AFDMQT 313 PM EST THU JAN 25 2007
.SHORT TERM DISCUSSION (TONIGHT)...
12Z RAOBS/WV IMAGERY AND RUC ANALYSIS SHOW HI AMPLITUDE TROF IN ERN
NAMERICA DOWNSTREAM OF RDG OVER THE ROCKIES. LES OVER THE FA
DOWNWIND OF LK SUP IN COLD NW FLOW BTWN ARCTIC HI PRES OVER ONTARIO
AND LO PRES IN THE LOWER GREAT LKS IS ON THE DIMINISHING TREND AS
VERY DRY/STABLE AIR SHOWN ON UPSTREAM 12Z RAOBS/TAMDAR SDNG FM CYQT
(INVRN BASE H925-95 AND PWAT AS LO AS 0.05 INCH) MOVES OVER THE UPR
LKS UNDER BLDG H5 HGTS/ INCRSG LARGER SCALE ACYC FLOW DESPITE SOME
LINGERING CNVGC ALG LK INDUCED TROFFING EXTENDING FM LO TO THE SE NW
ACRS LK HURON INTO ALGER COUNTY/CNTRL LK SUP. UPSTREAM...A SHRTWV
MOVING INTO NRN ALBERTA/SASKATCHEWAN IS TOPPING THE ROCKIES RDG.
QUITE A BIT OF MID CLD AND EVEN SOME PTCHY -SN NOTED FM SCNTRL CAN
INTO NE ND/NW MN IN THE SW FLOW/WAD PATTERN BTWN LO PRES ASSOCIATED
WITH THIS SHRTWV AND THE HI PRES SYS OVER ONTARIO AND THE UPR MS
RIVER VALLEY. PWAT 0.44 INCH AT YQD...SO THERE IS MORE MSTR AVBL TO
THIS SHRTWV.
MAIN FCST CONCERNS IN THE SHORT TERM ARE LINGERING LES TRENDS AND
-SN CHCS ASSOCIATED WITH SHRTWV NOW TOPPING ROCKIES RDG.
FOR TNGT...GUIDANCE SHOWS RISING HGTS OVER THE UPR GRT LKS IN
ADVANCE OF SHRTWV NOW OVER NRN ALBERTA/SASKATCHEWAN...WHICH IS FCST
TO REACH NR LK WINNIPEG BY 12Z FRI. AS HGTS RISE AND SFC RDG AXIS/
LOWER INVRN BASE/DEEPER DRY AIR PASSES ACRS THE CWA THIS EVNG UNDER
THE RISING HGTS...EXPECT LES TO DIMINISH AND THEN END WITH LTL
ADDITIONAL ACCUMULATION. WL LET ANY GOING HEADLINES EXPIRE AS
SCHEDULED. ALTHOUGH SKIES WL BE PCLDY FOR A TIME WITH ARRIVAL OF RDG
AXIS (EXCEPT OVER THE KEWEENAW WITH BKN-OVC SC LINGERING IN W-SW
FLOW EVEN ON BACK SIDE OF RDG)...NAM/GFS SHOW ISENTROPIC LIFT ON THE
280-290K SFCS OVERSPREADING THE FA QUICKLY AS SW RETURN FLOW DVLPS
IN THE WAKE OF DEPARTING SFC RDG. GFS IS MOST AGGRESSIVE AT PUSHING
HIER MID LVL MSTR TO THE E...AND USED ITS 280K SFC RH AOA 70 PCT TO
TIME ARRIVAL OF MID CLD AS THIS PROG APPEARS TO CORRELATE WELL WITH
OBSVD HI SC/LO AC CLD UPSTREAM. NAM FCSTS LLVLS BLO THE MID CLD DECK
REMAINING SO DRY THAT MODEL QPF IS ZERO...BUT GFS GENERATES SOME LGT
PCPN UNDER THE STRONGER ISENTROPIC LIFT AFT ABOUT 03Z OR SO OVER THE
W AND ACRS THE ENTIRE CWA AFT 06Z WITH ARRIVAL OF UPR DVGC IN RRQ OF
H3 JET MAX FCST TO MOVE OVER SE ONTARIO BY 12Z FRI. GFS FCST SDNGS
ARE QUITE A BIT MORE MOIST THRU MOST OF THE TROP IN LINE WITH OBSVD
12Z YQD SDNG...BUT MODEL FCST SDNGS DO SHOW LINGERING DRY LYR BTWN
H75-55...WHICH WOULD ALSO BE THE PRIME DENDRITIC SN GROWTH LYR.
CONSIDERING THIS DRY LYR AS WELL AS ANTECEDENT DRY AIR...LIMITED
COVG OF OBSVD SN UPSTREAM...AND NAM FCST...HAVE OPTED TO RETAIN POPS
BUT CUT VALUES FM HI CHC TO LWR CHC IN LINE WITH GFS MOS GUIDANCE.
AS FOR TEMPS...EXPECT MIN TEMPS RELATIVELY EARLY BEFORE THICKER MID
CLD/A BIT STRONGER SW FLOW DVLPS W-E AFT EARLY THIS EVNG.
KC
.LONG TERM (FRIDAY THROUGH THURSDAY)...
THE MAIN FORECAST CONCERN FOR THIS PORTION OF THE FORECAST REMAINS
THE LAKE EFFECT SNOW EVENT FOR LATE FRIDAY NIGHT THROUGH MUCH OF THE
WEEKEND.
ONCE AGAIN FOR THIS PERIOD...AM GENERALLY DISCOUNTING THE NAM...AS
IT IS OUT OF BOUNDS WHEN COMPARED TO THE GLOBAL MODELS. AS A
RESULT...HAVE LEANED THIS FORECAST CLOSER TO THE GFS SOLUTION.
GFS OFF OF BUFKIT IS PUTTING OUT OVER HALF AN INCH OF QFP OVER IWD
DURING THE NEXT 5 DAYS. CONTINUE TO MONITOR THE TRACK OF THE
SURFACE LOW...CURRENTLY CENTERED OVER THE SOUTHERN NORTHWEST
TERRITORIES SLIDING INTO NORTHERN SASKATCHEWAN. THIS LOW WILL SLIDE
SOUTHEASTWARD...AND OVER THE WESTERN HALF OF LAKE SUPERIOR BY FRIDAY
AFTERNOON AND THEN SOUTHEASTWARD OVER LAKE HURON BY 12Z SATURDAY.
THIS WILL FIRST ALLOW FOR A LONG SOUTHERLY FETCH ACROSS LAKE
MICHIGAN LATE FRIDAY MORNING THROUGH EARLY AFTERNOON (GENERALLY 2 TO
4 INCHES OF SNOW EXPECTED ACROSS THIS AREA FRIDAY)...AND THEN SWING
THE WINDS OUT OF A GENERALLY NORTH TO NORTHWESTERLY DIRECTION FRIDAY
NIGHT (AND KEEP THEM BETWEEN 300 AND 030 THROUGH TUESDAY). 850MB
TEMPERATURES...AFTER WARMING TO -7C OR SO FRIDAY WILL COOL DOWN TO
-12C ACROSS THE AREA BY 12Z SATURDAY...ALLOWING FOR A BETTER CHANCE
OF LAKE EFFECT OR LAKE ENHANCED SNOW. 850MB TEMPERATURES WILL THEN
SLOWLY COOL TO -20 TO -22C BY 06Z SUNDAY. GIVEN THIS...HAVE HOISTED
LAKE EFFECT SNOW WATCHES FOR GOGEBIC...ONTONAGON...MARQUETTE...AND
ALGER COUNTIES FOR SATURDAY MORNING THROUGH MID DAY SUNDAY.
FOR FRIDAY NIGHT HAVE ADJUSTED TEMPS DOWN A COUPLE OF DEGREES ACROSS
OUR CLIMATOLOGICALLY COOLER SOUTH CENTRAL CWA...WITH THE IDEA THAT
THE DRY SLOT MAY COME IN EARLY AND ALLOW TEMPS TO DROP. FIRST COLD
FRONT IS EXPECTED TO CROSS THE CWA LATE FRIDAY AFTERNOON THROUGH 06Z
SATURDAY. COOLER TEMPS ALOFT WILL TAKE A BIT LONGER TO SLIDE IN.
EXPECT THE SINGLE DIGITS TO LOW TEENS FOR HIGH TEMPERATURES
SUNDAY...AS THE COLDEST AIR SINKS OVERHEAD. WINDS BACK SLIGHTLY
SUNDAY...ADDING TO THE CONVERGENCE OVER THE EASTERN THIRD OF THE
LAKE SUPERIOR SHORELINE FROM MUNISING EAST. AS HAS BEEN THE TREND
OVER THE LAST COUPLE OF SHIFTS...HAVE INCREASED POPS HERE TO
DEFINITE. AS FOR RIGHT NOW...DO NOT HAVE ANY WATCHES/WARNINGS OR
ADVISORIES POSTED FOR THE EASTERN PORTIONS OF THE CWA (EXCEPT ALGER
COUNTY)...BUT AS THE TIME NEARS HEADLINES WILL LIKELY BE NEEDED.
MONDAY THROUGH THURSDAY (DAYS 4-7)...WITH THE RELATIVE CONSISTENCY
IN THE EXTENDED RANGE...WITH LESS MODEL FLIP FLOPPING THAN
USUAL...FEW CHANGES WERE MADE...PARTICULARLY TO TEMPERATURES.
STILL...DID COOL DOWN TEMPERATURES ROUGHLY 4 DEGREES ACROSS THE
BOARD MONDAY AFTERNOON. SO THE OVERALL PATTERN INCLUDES A SERIES OF
SHORTWAVES IN THE POLAR/ARCTIC JET CONTINUALLY RE-ENFORCING OUR
ALREADY COLD AIRMASS.
MONDAY 12Z...LOOKING AT THE MID LEVELS...THE GFS AND ECMWF BEGIN TO
BECOME A LITTLE MORE NOTICEABLE IN THERE DIFFERENCES. THE 500MB
DEPICTED BY THE GFS...ALTHOUGH SIMILAR IN STRENGTH IS ABLE TO SLIDE
FURTHER SOUTHWARD...MAKING IT INTO EASTERN LAKE HURON BY THIS
TIME...WHILE THE ECMWF HAS IT REMAINING OVER EASTERN HUDSON BAY. AS
PREVIOUSLY STATED...GENERALLY DISREGARDED THIS DISCREPANCY...AND
SIDED CLOSER TO THE GFS SOLUTION. UPDATED AND INCREASED CLOUD COVER
FOR MONDAY INTO MONDAY NIGHT...AS SHORTWAVE SLIDES IN FROM THE
NORTHWEST...ACCORDING TO THE 06Z GFS. ALTHOUGH IT SEEMS THAT THE
SHORTWAVE HAS DROPPED FURTHER SOUTH FOR THE 12Z GFS RUN...STILL
BELIEVE THAT WE WILL HAVE MORE THAN 40 PERCENT CLOUD COVER FOR THIS
PERIOD...SO HAVE KEPT THE ADJUSTED MORE PESSIMISTIC CLOUD FOR MONDAY
INTO MONDAY NIGHT.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
LAKE EFFECT SNOW WATCH FROM SATURDAY MORNING THROUGH SUNDAY
AFTERNOON FOR MIZ005-006.
LAKE EFFECT SNOW WATCH FROM LATE FRIDAY NIGHT THROUGH SUNDAY
MORNING FOR MIZ002-009.
&&
$$
.SHORT TERM...KC
.LONG TERM...KF
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
AFDMQT 1000 AM EST THU JAN 25 2007
.UPDATE...
12Z RAOBS/WV IMAGERY AND RUC ANALYSIS SHOW HI AMPLITUDE TROF IN ERN
NAMERICA DOWNSTREAM OF RDG OVER THE ROCKIES. LES CONTINUES OVER THE
FA DOWNSTREAM OF LK SUP IN COLD N FLOW BTWN HI PRES IN NW ONTARIO
AND LO PRES TROF EXTENDING FM LK HURON INTO CNTRL LK SUP. 12Z TAMDAR
SDNG FM SAW SHOWS INVRN AT H825 WITH BASE TEMP A CHILLY -25C. RUC
ANALYSIS SHOWS H85 THERMAL TROF OVER LK SUP ATTM. SPOTTER REPORT FM
EBEN JUNCTION IN WRN ALGER COUNTY INDICATES 8 INCHES FELL THERE
DURING THE NGT WHERE HEAVIER LES BAND LINGERED LONGER. REPORTS IN
GOGEBIC COUNTY/ERN MQT COUNTY SHOW 4-6 INCHES ACCUMULATION.
HOWEVER... THE OVERALL SHSN INTENSITY/COVG HAS BEEN DIMINISHED
SOMEWHAT BY VERY DRY/STABLE AIR UPSTREAM OVER ONTARIO ASSOCIATED
WITH THE ARCTIC HI PRES. SFC DWPTS -30F TO -40F WDSPRD OVER ONTARIO
N OF LK SUP...AND 12Z TAMDAR SDNG FM YQT AS WELL AS RAOBS FM INL/YPL
SHOW INVRN BASE H925-95 AND PWAT 0.05-0.10 INCH. IN FACT DESPITE
LLVL CNVGC ALG TROF IN ALGER COUNTY BTWN NW LAND BREEZE FM THE W AND
MORE NNE FLOW OVER THE E OFF ONTARIO...MQT 88D SHOWS LES BANDS HAVE
BECOME RATHER DISORGANIZED WITH IMPACT OF DRY/STABLE ADVCTN AS WELL
AS SOME DIRECTIONAL SHEAR IN THE SUB INVRN LYR DEPICTED ON MQT VWP.
FEW REFLECTIVITIES ABV 20DBZ REMAIN. SHORTER FETCH/LAND BREEZE FLOW
OFF ONTARIO HAVE PRETTY MUCH ENDED THE LES OVER THE FAR ERN CWA. SFC
TEMP IN CHIPPEWA COUNTY HAS FALLEN TO ARND -10F WITH DRIER FLOW.
MAIN FCST CONCERNS TDAY INVOLVE LES TRENDS/ADDITIONAL AMTS/GOING
HEADLINES.
FOR TDAY...GUIDANCE SHOWS HGT RISES BLDG HI PRES INTO THE UPR GRT
LKS. ARRIVAL OF MORE ACYC FLOW/LOWER INVRN HGT WL DIMINISH THE LES
W-E. IN FACT...EXPECT THE SHSN TO END OVER THE W AT IWD THIS AFTN AS
LLVL FLOW BACKS TO THE SW. GOING FCST HAS THESE LARGE SCALE TRENDS
WELL IN HAND...SO NEED TO MAKE ONLY MINOR ADJUSTMENTS TO FCST WX AND
SN AMTS. WL ALLOW GOING HEADLINES TO CONT/EXPIRE AS FCST. EXCEPT TO
BUMP UP FCST HI TEMPS AT A FEW PLACES MAINLY NR LK SUP BASED ON
CURRENT TEMPS...ONLY A FEW TWEAKS NECESSARY TO GOING MAX TEMPS FCST.
KC
.PREVIOUS DISCUSSION (ISSUED AT 404 AM)...
08Z WATER VAPOR LOOP AND RUC 500MB HEIGHT ANALYSIS SHOWED RIDGING
FROM SOUTHERN CALIFORNIA INTO NORTHERN ALBERTA WHILE UPPER TROUGHING
DOMINATED SE CANADA INTO THE GREAT LAKES. WITHIN THIS TROUGH...A
SHRTWV CAN BE SEEN DIVING SOUTHWARD THROUGH NORTHERN ONTARIO...NOW
NEAR WAWA. 850MB TEMPS ASSOCIATED WITH THIS SHRTWV APPEAR TO BE
AROUND -25C BASED ON 00Z RAOBS FROM MOOSONEE AND PICKLE LAKE.
ALTHOUGH THE AIR IS QUITE COLD WITH THE SHRTWV...VERY LITTLE IS
OCCURRING ON IR IMAGERY WITH IT DUE TO THE PRESENCE OF VERY DRY AIR
(PRECIPITABLE WATER OF 0.04 INCHES ON THE PICKLE LAKE SOUNDING).
SURFACE TEMPERATURES AND DEWPOINTS ALSO DEPICT THE SAME STORY OVER
NORTHERN ONTARIO...WITH READINGS WELL BELOW ZERO F. THE COLD AND DRY
AIR CONTINUES TO FLOW ACROSS LAKE SUPERIOR ON NORTHERLY WINDS
BETWEEN A 1032MB HIGH OVER NW ONTARIO AND A LOW PRESSURE TROUGH THAT
EXTENDS FROM LAKE ERIE TO SOUTHERN WISCONSIN. A LAKE INDUCED TROUGH
ALSO EXTENDS FROM LAKE ERIE NW TO NEAR ONTONAGON. PLENTY OF LAKE
EFFECT SNOW SHOWERS EXIST DUE TO THE COLD AIR FLOWING OVER 2-3C
WATER TEMPS. CURRENT RADAR IMAGERY SHOWS A FEW DISORGANIZED BANDS IN
ALGER AND EASTERN MARQUETTE COUNTIES...THOUGH THERE ARE A FEW 28DBZ
PIXELS WITHIN THEM. THERE WERE ALSO SOME INTENSE BANDS OCCURRING IN
THE FAR WESTERN U.P. OVERNIGHT...WITH THE BESSEMER AREA PICKING UP
AROUND 6 INCHES SINCE 7 PM CST PER THE COUNTY SHERIFF. HOWEVER...
OVER THE PAST FEW HOURS...THE SATELLITE APPEARANCE HAS GREATLY
DIMINISHED FOR THE LAKE EFFECT BANDS ON WESTERN LAKE SUPERIOR. TO
OUR NW...A 130 KT JET STREAK IS MOVING THROUGH WESTERN ONTARIO.
UPPER DIVERGENCE IN THE RIGHT ENTRANCE REGION IS HELPING SUPPORT
MID/HIGH CLOUDS OVER NORTHERN MANITOBA. THESE CLOUDS ARE ALSO
ASSOCIATED WITH A STRONG SHRTWV TROUGH WHICH CAN BE SEEN MOVING
ACROSS NORTHERN BRITISH COLUMBIA.
&&
.DISCUSSION...
MAIN FORECAST CONCERNS ARE WARM ADVECTION SNOW TONIGHT/FRI AND LES
EVENT FOR FRI NIGHT/SAT.
TODAY...SHRTWV NEAR WAWA WILL CONTINUE TO MAKE ITS WAY SOUTHWARD IN
THE MAINLY NORTHERLY FLOW ALOFT...REACHING SOUTHERN LAKE HURON BY
18Z. AS THIS SHRTWV PASSES...IT WILL CAUSE THE HIGH PRESSURE AREA
OVER NW ONTARIO TO BE PULLED DOWN INTO THE CWA BY 00Z. THEREFORE...
LES SHOULD BE ON A DIMINISHING TREND. IN FACT...THE LES IS EXPECTED
TO END IN THE WESTERN U.P. DUE TO A COMBINATION OF A CRASHING
INVERSION AND STRONG DRY AIR ADVECTION...DESPITE LAKE SURFACE TO
850MB DELTA-TS REMAINING AT OR ABOVE 16C. CURRENT LES TRENDS ON
WESTERN LAKE SUPERIOR SUPPORT THIS ASSESSMENT TOO. FOR THE NORTH
CENTRAL U.P....THE ENDING TREND WILL BE DOMINATED BY THE WIND
DIRECTION SINCE DELTA-TS ARE PROGGED AT OR ABOVE 20C AND THE LONGER
FETCH OF EASTERN LAKE SUPERIOR WILL MITIGATE THE MOISTURE.
HOWEVER...THE LAKE EFFECT WILL NOT BE AS GREAT AS IT WAS YESTERDAY
OR LAST NIGHT. WITH 850MB TEMPS REMAINING CHILLY...ONLY WARMING TO
-14C WEST OT -20C EAST...WILL CONTINUE TO STAY ON THE LOW END OF
GUIDANCE FOR TEMPS.
AS FAR AS HEADLINE CHANGES...DROPPED ADVISORY FOR SOUTHERN
SCHOOLCRAFT AS LITTLE IN THE WAY OF SNOWFALL APPEARS TO HAVE
OCCURRED THERE OVERNIGHT PER RADAR IMAGERY. ALL OTHER HEADLINES WILL
CONTINUE TO THEIR EXPIRATION TIMES.
TONIGHT...SHRTWV TROUGH CURRENTLY OVER NORTHERN BRITISH COLUMBIA IS
PROGGED TO DROP SE TO LAKE WINNIPEG BY 12Z FRI...WITH A 997MB LOW OR
SO LOCATED NEAR THE NE END. AS THIS OCCURS...A PORTION OF THE
WESTERN RIDGE WILL COME DOWN AHEAD OF THE TROUGH...CAUSING THE HIGH
PRESSURE AREA OVER UPPER MICHIGAN TO SLIDE EASTWARD. WARM ADVECTION
ON THE BACK SIDE OF THE HIGH/AHEAD OF THE SHRTWV TROUGH...COMBINED
WITH UPPER DIVERGENCE ASSOCIATED WITH THE 130KT JET STREAK CURRENTLY
IN MANITOBA MOVING TO LAKE HURON...WILL CAUSE A BAND OF MID CLOUDS
TO MOVE INTO THE CWA. INITIALLY...DRY LOW LEVELS SHOULD PREVENT
PCPN. HOWEVER...CONTINUED ISENTROPIC LIFTING/FRONTOGENETICAL FORCING
WILL CAUSE BASES TO LOWER AFTER MIDNIGHT...AND SOME LIGHT SNOW IS
EXPECTED TO DEVELOP. THERE STILL REMAINS SOME DISAGREEMENT ON THE
DEVELOPMENT OF THIS SNOW...THOUGH...AS NOTED BY NAM SOUNDINGS WHICH
SUGGEST THE DRIER LOW LEVELS WILL STAY FIRMLY IN PLACE. GIVEN THIS
DISAGREEMENT...AM HESITANT TO GO LIKELY YET...THOUGH WITH THE
CONSISTENCY OF THE GFS AND A LOCAL WRF-ARW RUN SHOWING A SIMILAR
SCENARIO TO THE GFS...FEEL AN UPGRADE TO 50 POPS IS WARRANTED.
TEMPERATURES ARE STILL TRICKY GIVEN THAT THERE WILL BE A FEW HOURS
IN THE EVENING WITH ONLY SOME HIGH CLOUDS AROUND. GOING FORECAST
MINS LOOK REASONABLE. READINGS SHOULD CLIMB AFTER MIDNIGHT WITH
RETURN FLOW AND INCOMING WARM ADVECTION PCPN.
FRI...SHRTWV TROUGH WILL CONTINUE MOVING SE...REACHING MINNESOTAS
INTERNATIONAL BORDER AROUND 00Z. THE SURFACE LOW ASSOCIATED WITH THE
TROUGH IS PROGGED TO MOVE INTO THE WESTERN U.P.. BAND OF WARM
ADVECTION SNOW WHICH IS EXPECTED OVER THE WEST HALF OF THE U.P. IN
THE MORNING WILL PUSH EAST THROUGH THE DAY...PERHAPS GETTING
ENHANCED BY A LAKE MICHIGAN LAKE EFFECT BAND. BEHIND THE WARM
ADVECTION SNOW...A DRY SLOT IS PROGGED TO COME IN ALOFT. SOME
CONCERN EXISTS THAT THE SNOW MAY TAPER OFF TO FREEZING DRIZZLE...BUT
RIGHT NOW THE -10C LAYER STILL REMAIN SATURATED...SO THE SNOW MAY
JUST TO TAPER OFF TO FLURRIES OR NOTHING AT ALL. FOR NOW WILL
MAINTAIN A CHANCE OF SNOW INTO THE AFTERNOON...BUT HAVE MUCH LOWER
QPF VALUES THEN. HAVE RAISED TEMPERATURES SLIGHTLY IN THE WESTERN
U.P. GIVEN THAT GUIDANCE HAS WARMED UP IN THIS AREA. OTHERWISE...THE
REST OF THE HIGH TEMP FORECAST LOOKS REASONABLE.
FRI NIGHT AND SAT...DURING THIS PERIOD...THE SHRTWV TROUGH IS
PROGGED BY ALL MODELS TO SWING THROUGH THE CWA. COLD AIR ADVECTION
AT 850MB SHOULD ALREADY BE GOING ON FRI EVENING...WITH 850MB TEMPS
FALLING TO -12 TO -14C BY 06Z...WHICH SHOULD BE ENOUGH TO GET LAKE
EFFECT GOING...ESPECIALLY IN THE WESTERN U.P. GIVEN THE PROGGED WNW
LOW LEVEL WIND FLOW. LAKE EFFECT WILL ALSO GET SOME SYNOPTIC SUPPORT
DUE TO DPVA AHEAD OF THE SHRTWV TROUGH. HAVE INCLUDED A FEW INCHES
OF SNOWFALL...HOWEVER IF THE TROUGH COMES IN FASTER...AT LEAST
ADVISORY LEVEL SNOWFALL SHOULD BE MET FOR FRI NIGHT. SINCE IT LOOKS
CERTAIN THAT SOME LAKE EFFECT WILL OCCUR IN THE WESTERN U.P....HAVE
RAISED POPS TO CATEGORICAL. THINGS GET A LITTLE MORE INTERESTING ON
SAT. ON SAT...AS THE SHRTWV TROUGH AND ITS ACCOMPANYING MID-LEVEL
MOISTURE MOVES ACROSS...A SECONDARY SURFACE COLD FRONT ASSOCIATED
WITH THE SHRTWVS SURFACE LOW IS PROGGED TO DROP SOUTH ACROSS LAKE
SUPERIOR. GIVEN THAT 850MB TEMPS COOL A FEW MORE DEGREES C...
RESULTING IN PLENTY OF OVER-WATER INSTABILITY...THERE WILL LIKELY BE
A SIGNIFICANT CONVERGENT LAKE EFFECT BAND ALONG THE FRONT. WOULD NOT
BE SURPRISED TO SEE A COUPLE OF INCHES OF SNOW FALL OUT OF THIS BAND
ACROSS ALL OF THE NORTHERN U.P.. GFS FORECAST SOUNDINGS ARE PRETTY
IMPRESSIVE WHEN THE BAND COMES THROUGH...INDICATING SATURATED
CONDITIONS UP TO 15000 FT AND THE ONLY INVERSION BEING THAT OF THE
TROPOPAUSE. IN ADDITION...NORTHERLY WINDS BEHIND THE FRONT...ALONG
WITH PLENTY OF LOW TO MID LEVEL MOISTURE AROUND SHOULD SUPPORT MORE
INTENSE MULTI-PARALLEL BANDS THAN THOSE TODAY. GIVEN THE CONSISTENCY
FROM THE MODELS PREDICTING THIS EVENT...HAVE INCREASED POPS TO
CATEGORICAL. IN FACT...HAVE EVEN INCLUDED THE WORDING OF HEAVY AT
TIMES FOR THE FAR WESTERN U.P. AS THIS AREA WILL SEE STRONG LOW
LEVEL CONVERGENCE ALL DAY. HAVE ADJUSTED QPF/SNOW AMOUNTS UPWARD TO
NEAR WARNING CRITERIA FOR THE FAR WESTERN U.P. WITH THE REST OF THE
NORTHERN U.P. AT ADVISORY LEVEL. FOR NOW...THE EVENT WILL CONTINUE
TO BE HIGHLIGHTED IN THE HWO...BUT FUTURE SHIFTS WILL LIKELY NEED TO
ISSUE WATCHES...WARNINGS AND/OR ADVISORIES.
SAT NIGHT AND SUN...GFS/UKMET/ECMWF INDICATE THAT AFTER THE PASSAGE
OF SATURDAYS SHRTWV TROUGH...ANOTHER SHRTWV WILL DIVE SOUTHWARD
THROUGH MINNESOTA AND INTO ILLINOIS. MOISTURE ASSOCIATED WITH THIS
SHRTWV LOOKS TO STAY TO THE WEST OF HERE...THEREFORE WITH 850MB
TEMPS COOLING INTO THE LOW -20S C...DRY AIR ADVECTION AND LOWERING
INVERSIONS...THE LAKE EFFECT SNOW WILL BE ON A DIMINISHING TREND
THROUGH THIS PERIOD. OTHERWISE...WITH THE COOLER 850MB
TEMPS...READINGS WHICH WILL BE CLOSE TO NORMAL FOR FRI AND SAT WILL
GO BACK TO BELOW NORMAL.
BEYOND SUN...LOOKS LIKE THE PATTERN WILL REMAIN COLD WITH PERIODS OF
LAKE EFFECT SNOW. LOOKING FARTHER OUT TOWARDS THE BEGINNING OF
FEBRUARY...THERE HAS BEEN A LOT OF CONSISTENCY WITH PAST GFS AND
ECMWF RUNS...INCLUDING THOSE TODAY...SUGGESTING A COLDER ARCTIC
AIRMASS TO MOVE INTO THE CWA WITH 850MB TEMPS AROUND THE -30C MARK.
WILL WAIT AND SEE IF THIS OCCURS...BUT GIVEN THE CONSISTENCY...IT
BEARS WATCHING.
COORD WITH GRB AND HPC...THANKS.
AJ
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
LAKE EFFECT SNOW WARNING FOR MIZ006 UNTIL 22Z.
LAKE EFFECT SNOW ADVISORY FOR MIZ005-013 UNTIL 18Z.
LAKE EFFECT SNOW ADVISORY FOR MIZ002-009 UNTIL 12Z.
LAKE EFFECT SNOW ADVISORY FOR MIZ085 UNTIL 22Z.
&&
$$
AREA FORECAST DISCUSSION
NWS GRAND FORKS ND
AFDFGF 429 AM CST THU JAN 25 2007
.SHORT TERM...
UPPER LEVEL RIDGE OVER THE NORTHERN ROCKIES WILL SHIFT OVER THE
REGION AND MAKE FOR A RELATIVELY MILD DAY. HOWEVER TEMPS STARTING
OUT COLD IN THE NORTHEAST ZONES. UPPER LEVEL LOW OVER WESTERN CANADA
WILL MOVE OVER SOUTHERN CANADA FRI NIGHT WITH 200 METER HEIGHT FALLS
FORECAST. GOOD WARM ADVECTION SHOULD OCCUR EAST OF UPPER LOW.
TAMDAR SOUNDINGS SHOW HIGHER TEMPERATURES AND HIGHER MID LEVEL
MOISTURE OVER WESTERN ZONES THAN IN THE EASTERN ZONES. CANADIAN
RADAR SHOWING SOME RETURNS ALONG SOUTHERN MANITOBA MOVING SOUTHEAST
IN AREA OF BEST LOW LEVEL WARM ADVECTION. FEW RETURNS ON KMVX OVER
NORTHWEST ZONES ALSO MOVING SOUTHEAST. SOME 850 AND 700 HPA
FRONTOGENESIS NOTED ALONG NORTHERN BORDER TODAY. WILL ADD CHANCE
FOR DUSTING OF SNOW TODAY MAINLY IN THE NORTHERN VALLEY.
HAVE RAISED TEMPS FOR FRI NIGHT AS MODELS EXPECT LOW LEVEL ADIABATIC
CONDITIONS FRI NIGHT THROUGH SAT MORNING.
.LONG TERM...
TEMPERATURES TWEAKED.
&&
.FGF WATCHES/WARNINGS/ADVISORIES...
ND...NONE.
MN...NONE.
&&
$$
HOPPES