Forecast Discussions mentioning "ACARS", "MDCRS", "AIRCRAFT", "TAMDAR", or "AMDAR" received at FSL on 03/25/07

AREA FORECAST DISCUSSION
NWS SAN DIEGO CA
137 PM PDT FRI MAR 23 2007 .SYNOPSIS... AN UPPER LEVEL LOW WILL CONTINUE TO MOVE EAST ACROSS SONORA MEXICO TONIGHT. A HIGH PRESSURE RIDGE WILL BUILD OVER SOUTHERN CALIFORNIA THROUGH THE WEEKEND. A COASTAL EDDY WILL DEVELOP TONIGHT AND BE PRESENT DURING THE NIGHT AND MORNING HOURS THROUGH SUNDAY. ON MONDAY THE HIGH PRESSURE RIDGE WILL BREAK DOWN. ON TUESDAY A STORM SYSTEM MOVING INLAND TO THE NORTH. THIS WILL BRING GUSTY WINDS...COOLER TEMPERATURES...AND A CHANCE OF RAIN AND MOUNTAIN SNOW TO SOUTHERN CALIFORNIA. FAIR WEATHER AND A SLOW WARMING TREND ARE EXPECTED FOR THE LATTER HALF OF NEXT WEEK AS HIGH PRESSURE REBUILDS. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... .SHORT TERM (TONIGHT THROUGH MONDAY)... LOW MOVING OFF TO THE EAST AND SUBSIDENCE ALOFT FROM RIDGE BUILDING IN HAS CAPPED CONVECTION OVER SOUTHWEST CALIFORNIA. OVER CONVECTION. LEFT A MENTION OF SHOWERS OVER THE EAST SLOPES FOR THIS EVENING BUT CHANCE OF MEASURABLE AMOUNTS ARE PRETTY SLIM. SOUTHERLY WINDS AT COASTAL STATIONS SUPPORT EDDY DEVELOPMENT AND NAM12 MODEL INDICATES IT WILL PRESENT DURING THE NIGHT AND MORNING HOURS WITH ONSHORE FLOW IN THE AFTERNOONS. THE RIDGE ALOFT WILL BE BUILDING AT THE SAME TIME AND THE 1000-500 MB THICKNESS INCREASES SUPPORT ABOUT 3 TO 5 DEGREES WARMING EACH DAY...BUT DO NOT EXPECT TO SEE ANY WARMING OVER INLAND VALLEYS AND LIKELY COOLING OVER COASTAL SECTIONS DUE TO INCREASE IN STRATUS. ON MONDAY THE RIDGE IS FLATTENED AS LONG WAVE TROUGH ADVANCES TOWARDS COAST. THIS SHOULD BRING THICKENING AND LOWERING CIRROSTRATUS CLOUDS AND LIFTING OF THE STRATUS CLOUDS TO THE LOWER COASTAL SLOPES...RESULTING IN A GENERAL COOL DOWN FOR ALL AREAS. && .LONG TERM (TUESDAY THROUGH FRIDAY)... FOR TUESDAY THE TROUGH MOVES INLAND TO THE NORTH. MAIN EFFECT ON SOUTHERN CALIFORNIA EXPECTED TO BE STRONG GUSTY WINDS...ABOUT 20 DEGREES COOLING...AND A SLIGHT CHANCE OF RAIN AND MOUNTAIN SNOW. HAVE SNOW LEVEL LOWERING TO 4000-4500 FEET ON TUESDAY. FOR WEDNESDAY HIGH PRESSURE REBUILDS BUT REGION STILL IN COOL NORTHWEST FLOW. FOR THURSDAY AND BEYOND THE MEDIUM RANGE MODELS GO OUT OF PHASE. WILL STAY WITH SCENARIO OF WEAK HIGH PRESSURE REBUILDING THROUGH FRIDAY...FOR SLOW WARM UP BACK TO SEASONAL TEMPERATURES. && .AVIATION... 231900Z...LATE MORNING ACARS SOUNDINGS INDICATE THE MARINE LAYER DEPTH NEAR KSAN WAS AROUND 1000 FEET. A MODERATE COASTAL EDDY OVER THE COASTAL WATERS WILL HELP MAINTAIN THE MARINE LAYER THROUGH SATURDAY. AN AREA OF STRATUS ALONG THE SOUTHERN ORANGE COUNTY AND NORTHERN SAN DIEGO COUNTY COASTLINE SHOULD EXPAND THIS EVENING AND PUSH INLAND. BASES OF THE STRATUS SHOULD BE AROUND 800 FEET MSL SO AS THE STRATUS PUSHES INLAND...EXPECT IFR CEILINGS AT MOST COASTAL AIRPORTS TONIGHT WITH LIFR CEILINGS POSSIBLE AT SOME OF THE MESA AND INLAND VALLEY AIRPORTS. STRATUS SHOULD STAY AWAY FROM THE KONT AREA BUT SOME RADIATIONAL FOG MAY DEVELOP IN THE VICINITY OF KONT...ESPECIALLY AROUND KCNO BEFORE SUNRISE ON SATURDAY. ABOVE THE MARINE LAYER...MID AND HIGH LEVEL WRAP AROUND MOISTURE SHOULD CONTINUE TO DIMINISH THROUGH TONIGHT AS THE UPPER LOW CURRENT OVER NORTHWEST SONORA IN MEXICO CONTINUES TO DRIFT SLOWLY TO THE EAST. BASES SHOULD REMAIN ABOVE 12000 FEET MSL. && .SGX WATCHES/WARNINGS/ADVISORIES... CA...NONE. PZ...NONE. && $$ PUBLIC/FIRE WEATHER...BALFOUR AVIATION/MARINE.......HORTON NWS ON THE WEB AT WEATHER.GOV/SANDIEGO
AREA FORECAST DISCUSSION
NWS TAUNTON MA
1025 PM EDT SAT MAR 24 2007 .UPDATE... RAIN HAS MIXED WITH OR CHANGED TO SNOW MOST PLACES NORTH AND EAST OF A WINDSOR LOCKS-WILLIMANTIC LINE...MEANWHILE THE BACK EDGE OF PRECIP ON THE ALY RADAR IS MOVING INTO THE BERKSHIRES IN THE SOUTH AND WILL REACH THE GREEN MOUNTAINS IN THE NORTH...AND SHOULD MOVE EAST OF MASSACHUSETTS BY 06Z WITH A FEW WIDELY SCATTERED SNOW SHOWERS POSSIBLE AFTER THE MAIN AREA MOVES EAST. HAVE ADJUSTED THE FORECAST TO THIS TIMING AND REMOVED FURTHER MENTION OF SLEET. ASIDE FROM PRECIP TIMING AND COOLING TEMPS A COUPLE OF DEGREES...NO MAJOR CHANGES PLANNED IN THE FORECAST. && .PREV DISCUSSION... /ISSUED 809 PM EDT SAT MAR 24 2007/ UPDATE... KBOX RADAR SHOWING 40+ DBZ OVER NORTHERN CONNECTICUT. CROSS SECTIONS SHOW THESE 40+ DBZ ALL AROUND AND BELOW 10 THOUSAND FEET WITH 20 DBZ BELOW 20 THOUSAND FEET. BDL REPORTED 0.12 RAINFALL BETWEEN 7 AND 8 PM. AMDAR AIRCRAFT DESCENT SOUNDING INTO BDL AT 7 PM SHOWED AN ISOTHERMAL LAYER AROUND 0C FROM 3000 FEET TO 10000 FEET. AT THE MOMENT THIS LAST SENTENCE WAS BEING WRITTEN...TWO REPORTS OF SLEET CAME IN FROM HARTFORD AND ATTLEBORO. WILL AMEND FORECAST TO INCLUDE OCCASIONAL SLEET FOR AREAS SOUTH OF THE MASS PIKE WHERE THE HIGHER DBZ ARE SHOWING. NO OTHER CHANGES AT THIS MOMENT. PREV DISCUSSION... /ISSUED 450 PM EDT SAT MAR 24 2007/ .STILL EXPECTING A 2 TO 5 INCH SNOWFALL ACROSS INTERIOR TONIGHT WITH GREATEST AMOUNTS IN HIGHER ELEVATIONS... SHORT TERM /TONIGHT THROUGH SUNDAY NIGHT/... CLOUD SHIELD CONTINUES TO MAKE STEADY EASTWARD PROGRESS AND WILL OVERSPREAD SOUTHERN NEW ENGLAND BY EARLY EVENING. RADAR MOSAIC HAS LEADING EDGE OF SHOWERS INTO NORTHERN NY AND EVEN ADJACENT PARTS OF NORTHERN NEW ENGLAND...BUT MOST OF THIS IS ALOFT. RAIN IS REACHING GROUND FARTHER W NEAR WATERTOWN AND SYRACUSE. WE ARE CONTINUING SNOW ADVISORY FOR TONIGHT...BUT WE HAVE NUDGED TOTALS UP SLIGHTLY OVER INTERIOR NE MA WHICH MEANS WE WILL ADD CENTRAL MIDDLESEX COUNTY MA TO ADVISORY AT THIS TIME. 12Z NAM/GFS ARE IN GENERAL AGREEMENT IN HANDLING OF POTENT SHORT WAVE AND ASSOCIATED SURFACE LOW DIVING SE FROM GREAT LAKES TONIGHT. WE ARE LEANING MORE TOWARD NAM FOR DETAILS GIVEN ITS BETTER RESOLUTION SINCE ELEVATION WILL PLAY A LARGE ROLE IN RAIN VS SNOW AS WELL AS SNOWFALL TOTALS. WE DO THINK NAM IS A BIT OVERDONE WITH ITS QPF OF 0.50 TO 0.75 INCH ACROSS MUCH OF NORTHERN MA AND SW NH...ESPECIALLY WHEN COMPARED WITH 09Z SREFS WHICH ONLY SUPPORT 0.25 TO 0.50 INCH. HOWEVER THEY DO AGREE THAT AXIS OF MAX QPF WILL BE ACROSS OUR NORTHERN ZONES...WITH LESSER AMOUNTS OF 0.10 TO 0.25 INCH S OF MASS PIKE. WE HAVE WARMED UP NICELY THIS AFTERNOON WITH ALL LOCATIONS WELL UP INTO THE 40S AND LOWER 50S. IT IS THIS LOW LEVEL WARMING THAT WILL BE KEY PLAYER IN HOW FAST WE SEE A CHANGEOVER FROM RAIN TO SNOW...SINCE ALOFT IT IS STILL FAIRLY COLD AND WILL EASILY SUPPORT SNOW AT ONSET. THIS IS A TYPICAL SPRING SNOWFALL EVENT WHERE HIGHER ELEVATIONS ARE FAVORED...BUT SINCE SNOW WILL BE FALLING AT NIGHT WE STAND TO SEE SOME ACCUMULATION AT LOWER ELEVATIONS AS WELL. IN ORDER TO SEE MORE WIDESPREAD ADVISORY TOTALS...WE WOULD LIKE TO SEE STRONGER LIFT ARRIVING AFTER MIDNIGHT...BUT SINCE IT IS COMING IN DURING FIRST PART OF NIGHT...THAT SHOULD LIMIT EXTENT OF 2 TO 4 INCH TOTALS. AS A RESULT...WE EXPECT LIGHT RAIN TO MOVE INTO SOUTHERN NEW ENGLAND THIS EVENING...POSSIBLY MORE OF A RAIN/SNOW MIX AT HIGHER ELEVATIONS... BEFORE CHANGING TO SNOW WITHIN A FEW HOURS OF ONSET. IN ADDITION TO WET BULB COOLING...WE ALSO HAVE STRONG LIFT ENTERING PICTURE AS A RESULT OF APPROACHING MID LEVEL SHORT WAVE...WHICH WILL ALSO ACT TO COOL DOWN COLUMN FAIRLY QUICKLY. THIS CHANGEOVER WILL TAKE PLACE BY 9 OR 10 PM ACROSS SW NH AND WESTERN/CENTRAL MA...BUT PROBABLY NOT UNTIL 11 PM OR MIDNIGHT FARTHER S AND E INTO NORTHERN CT...NORTHERN RI AND EASTERN MA...AND MORE LIKE 1 TO 2 AM NEAR S COAST. ALTHOUGH THIS SYSTEM IS PROGRESSIVE AND WILL EXIT REGION QUICKLY... THERE WILL BE A 3 TO 4 HOUR PERIOD WHERE EVERYTHING COMES TOGETHER TO PRODUCE DECENT SNOWFALL RATES...ESPECIALLY AT HIGHER ELEVATIONS WHERE SNOW WILL BE MORE PROLONGED AND OVER OUR NORTHERN ZONES WHERE CROSS SECTIONS INDICATE MAX SNOW GROWTH ZONE WILL BE. WHILE WE DO NOT SEE SNOWFALL TOTALS IN EXCESS OF 6 INCHES IN OUR HIGHER ELEVATION SITES...WE SHOULD BE ABLE TO GET WIDESPREAD 3 TO 5 INCH TOTALS FROM MONADNOCKS TO E SLOPES OF BERKSHIRES AND WORCESTER HILLS WITH 2 TO 4 INCHES ELSEWHERE ACROSS INTERIOR. FARTHER S INTO NORTHERN CT...NORTHERN RI AND INTERIOR EASTERN MA... WE THINK INITIAL LOW LEVEL WARMING WILL PLAY MORE OF A ROLE AND LIMIT SNOWFALL ACCUMULATIONS TO 1 TO 3 INCHES...MAINLY ON GRASS...SINCE RAIN/SNOW MIX SHOULD LAST A BIT LONGER AND BEST LIFT IS CENTERED IN WARMER AIR. SOME OF HIGHER ELEVATIONS OF HARTFORD...TOLLAND...WINDHAM AND PROVIDENCE COUNTIES COULD SEE AS MUCH AS 3 TO 4 INCHES LOCALLY...BUT WE DO NOT THINK THESE TOTALS WILL BE WIDESPREAD ENOUGH TO JUSTIFY ADVISORIES AT THIS TIME. SYSTEM WILL ALREADY BE OFFSHORE SUN MORNING...SO SNOW SHOULD BE OVER 4 TO 6 AM SUN. LOW LEVEL MOISTURE WILL HANG ON INTO MORNING PER CROSS SECTIONS...BEFORE DRYING SETS IN DURING MIDDAY AND AFTERNOON AND ALLOWS FOR SKIES TO CLEAR. TEMPERATURES SHOULD RECOVER NICELY SUN AFTERNOON...WELL INTO 40S IF NOT 50F AT A FEW SPOTS S OF MASS PIKE. WEAK HIGH PRESSURE BUILDS INTO REGION SUN NIGHT WITH ONLY PATCHY HIGH CLOUDS EXPECTED. LONG TERM /MONDAY THROUGH SATURDAY/... MEDIUM RANGE MODELS SHOWED PRETTY GOOD CONTINUITY THIS AFTERNOON... AT LEAST THE GFS SUITE AND BOTH THE GFS AND ECMWF ENSEMBLES. ALSO...BEYOND THURSDAY...MODELS SHOWING MORE SPREAD AMONG MANY OF THE SUITE MEMBERS...SO NOT A LOT OF CONFIDENCE WITH NEXT APPROACHING SYSTEM OUT OF THE MIDWEST LATE NEXT WEEK. USED MAINLY THE ENSEMBLES AND 00Z GFS FOR THIS PORTION OF THE FORECAST. HIGH PRESSURE WILL BUILD OFF THE SOUTH COAST MONDAY...HELPING SHIFT WINDS AROUND TO SOUTHWEST. WILL PROBABLY NOT FEEL THE FULL EFFECTS OF WARMER TEMPERATURES...BUT HIGHS IN THE 50S WILL FEEL NICE THOUGH REMAINING CHILLY ALONG THE SOUTH COAST. WARM FRONT DEVELOPS ACROSS THE GREAT LAKES DURING MONDAY...WITH AREA OF PRECIP QUICKLY PUSHING EAST. THERE WERE TIMING ISSUES THIS WARM FRONT AND A WEAK AREA OF LOW PRESSURE THAT MAY DEVELOP ALONG WITH IT FOR THE MONDAY NIGHT-TUESDAY TIMEFRAME. THE NAM/WRF WAS A GOOD 6-9 HOURS SLOWER THAN THE GFS RUN. HARD TO EXPLAIN...AS THE FORECASTED UPPER FLOW ON BOTH MODELS APPEARS IN LINE AS A WEAKENING UPPER SHORT WAVE RIDES OVER THE UPPER LEVEL RIDGE IN THE MIDWEST. DO NOTE THAT THE GFS IS A LITTLE FASTER AND STRONGER AS IT MOVES THROUGH. STILL A PRETTY FAST UPPER LEVEL FLOW...WHICH ALSO HELPS EXPLAIN THE TIMING DIFFERENCES. USED A BLEND OF THESE MODELS FOR TIMING THIS SYSTEM INTO THE REGION...AS THIS SYSTEM WILL BE ANOTHER FAST MOVER /SIMILAR TO TONIGHTS LOW/. LITTLE IF ANY COLD AIR TO WORK WITH...SO EXPECT THE PRECIP TO BE ALL RAIN AS IT APPROACHES LATE MONDAY...MOVING THROUGH TUESDAY MORNING. FORECASTED LOW MONDAY NIGHT COULD ACTUALLY RUN A FEW DEGREES ABOVE NORMAL WITH THIS LOW WITH SOME WARM AIR ADVECTION RIDING IN. ONCE THE LOW AND FRONT PUSH OFF THE COAST MIDDAY TUESDAY...CLOUDS WILL SLOWLY BREAK UP WITH DAYTIME HIGHS SOARING TO AROUND 60 DEGREES. THE OFFSHORE HIGH WILL BREAK DOWN AND HEAD EAST...WHILE ANOTHER HIGH BUILDS SOUTHEAST OUT OF CENTRAL CANADA BY WEDNESDAY MORNING. NOT MUCH WEATHER ASSOCIATED WITH THIS...BUT DO NOTE A SLIGHT COOLING TREND FOR THE MIDDLE OF NEXT WEEK. ANOTHER STRONGER LOW TAKES SHAPE OVER THE ROCKIES AROUND MIDWEEK. THE MODEL SUITE HAD A HANDLE ON THIS LOWS DEVELOPMENT...BUT HAVE A LOT OF ISSUES WITH THE TIMING OF THE SYSTEM AS IT TREKS ACROSS THE NORTHERN TIER FOR LATE NEXT WEEK. APPEARS THAT...FOR NOW...WILL CONTINUE WITH DRY WEATHER BUT A SLOW COOLING TREND AS THE CANADIAN HIGH TAKES HOLD. UPPER RIDGE BUILDS OVER THE GREAT LAKES AND MIDWEST...WHICH MAY HOLD THE WESTERN LOW AT BAY UNTIL LATE NEXT WEEK. CURRENT THINKING IS TO BRING IN A LOW CHANCE OF SHOWERS FOR FRIDAY NIGHT AND NEXT SATURDAY. AVIATION /18Z-18Z/... CONDITIONS LOWER TO MVFR IN CT VALLEY 00Z-02Z AND ON COASTAL PLAIN BY 04Z SUN AS PRECIPITATION SPREADS INTO REGION AHEAD OF CLIPPER LOW DIVING SE FROM GREAT LAKES. INITIALLY MOST LOCATIONS WILL HAVE RAIN...OR A RAIN/SNOW MIX ACROSS INTERIOR...BEFORE A TRANSITION TO SNOW 02Z-06Z AT ALL TERMINALS. EXCEPTION IS ON CAPE COD AND ISLANDS WHERE WE THINK IT WILL STAY AS A MIX OF RAIN AND SNOW. ALTHOUGH MVFR WILL DOMINATE TONIGHT WE DO EXPECT A PERIOD OF IFR OVERNIGHT...ESPECIALLY 03Z-07Z...BEFORE CONDITIONS SLOWLY IMPROVE AS PRECIPITATION MOVES OFFSHORE. HIGHER TERRAIN AIRPORT SUCH AS KORH SHOULD DROP TO LIFR...AS ARE MANY OF OUR SW NH AIRPORTS INCLUDING KMHT WHERE HEAVIEST SNOWFALL IS EXPECTED. WINDS NOT FORECAST TO BE AN ISSUE WITH THIS SYSTEM. LIGHT OR ONSHORE WINDS WILL BACK TO E/NE TONIGHT AND N/NE SUN...WITH SPEEDS AOB 10KT. MVFR TO START OFF SUN...BEFORE LIFTING TO VFR AROUND MIDDAY AS SKIES CLEAR OUT. OUTLOOK 18Z SUN TO 12Z MON...VFR WITH MOSTLY CLEAR SKIES AND LIGHT WINDS. MARINE... LOCAL SEA BREEZES WILL GIVE WAY TO E/NE WINDS TONIGHT...BUT AOB 10KT ON ALL WATERS. RAIN WILL MOVE INTO REGION THIS EVENING...AND WILL CHANGE TO SNOW LATER TONIGHT BEFORE ENDING BY DAYBREAK SUN. NE FLOW TRIES TO STRENGTHEN ON S COASTAL WATERS SUN MORNING AS LOW PRESSURE PASSES OFFSHORE...BUT WE EXPECT WINDS AND SEAS TO REMAIN BELOW SMALL CRAFT ADVISORY LEVELS. WEAK HIGH PRESSURE BUILDS OVER WATERS SUN AND SUN NIGHT. IN THE LONG TERM...HIGH PRESSURE IN CONTROL ON MONDAY...THOUGH SOUTHWEST WINDS WILL GUST UP TO 20 KTS LATE IN THE DAY AND MONDAY NIGHT AS WEAK LOW PRESSURE AND FRONT APPROACH. WINDS WILL SLOWLY SHIFT TO WEST AND NORTHWEST DURING TUESDAY AS LOW CLEARS THE COAST. HIGH PRESSURE TAKES OVER FROM CENTRAL CANADA FOR WEDNESDAY AND THURSDAY...WITH A NORTH TO NORTHWEST FLOW. WILL KEEP WIND GUSTS UP TO 20 KTS. BUT NOT IMPRESSIVE COLD AIR ADVECTION NOR GOOD PRESSURE GRADIENT AT THIS POINT SO WILL KEEP BELOW SMALL CRAFT...AT LEAST ON THE WINDS. WNA WAVEWATCH III MODEL TRIES TO BRING SEAS UP TO NEAR OR ABOVE 5 FEET ON THE FLOW AHEAD OF THE LOW AND FRONT MONDAY THROUGH TUESDAY NIGHT. WENT ABOUT 1 OR 2 FEET BELOW GUIDANCE. FELT THEY WERE OVERDONE WITH THE SOUTHWEST FLOW...BUT STILL CLOSE TO OR ABOVE SMALL CRAFT CRITERIA FOR A TIME...UPWARDS TO 6 FEET ON THE OUTER WATERS BOTH AHEAD AND BEHIND THE LOW AND FRONT. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...SNOW ADVISORY UNTIL 4 AM EDT SUNDAY FOR MAZ002>005-008>010-012- 026. NH...SNOW ADVISORY UNTIL 4 AM EDT SUNDAY FOR NHZ011-015. RI...NONE. MARINE...NONE. && $$ UPDATE...
AREA FORECAST DISCUSSION
NWS TAUNTON MA
809 PM EDT SAT MAR 24 2007 .UPDATE... KBOX RADAR SHOWING 40+ DBZ OVER NORTHERN CONNECTICUT. CROSS SECTIONS SHOW THESE 40+ DBZ ALL AROUND AND BELOW 10 THOUSAND FEET WITH 20 DBZ BELOW 20 THOUSAND FEET. BDL REPORTED 0.12 RAINFALL BETWEEN 7 AND 8 PM. AMDAR AIRCRAFT DESCENT SOUNDING INTO BDL AT 7 PM SHOWED AN ISOTHERMAL LAYER AROUND 0C FROM 3000 FEET TO 10000 FEET. AT THE MOMENT THIS LAST SENTENCE WAS BEING WRITTEN...TWO REPORTS OF SLEET CAME IN FROM HARTFORD AND ATTLEBORO. WILL AMEND FORECAST TO INCLUDE OCCASIONAL SLEET FOR AREAS SOUTH OF THE MASS PIKE WHERE THE HIGHER DBZ ARE SHOWING. NO OTHER CHANGES AT THIS MOMENT. && .PREV DISCUSSION... /ISSUED 450 PM EDT SAT MAR 24 2007/ ..STILL EXPECTING A 2 TO 5 INCH SNOWFALL ACROSS INTERIOR TONIGHT WITH GREATEST AMOUNTS IN HIGHER ELEVATIONS... SHORT TERM /TONIGHT THROUGH SUNDAY NIGHT/... CLOUD SHIELD CONTINUES TO MAKE STEADY EASTWARD PROGRESS AND WILL OVERSPREAD SOUTHERN NEW ENGLAND BY EARLY EVENING. RADAR MOSAIC HAS LEADING EDGE OF SHOWERS INTO NORTHERN NY AND EVEN ADJACENT PARTS OF NORTHERN NEW ENGLAND...BUT MOST OF THIS IS ALOFT. RAIN IS REACHING GROUND FARTHER W NEAR WATERTOWN AND SYRACUSE. WE ARE CONTINUING SNOW ADVISORY FOR TONIGHT...BUT WE HAVE NUDGED TOTALS UP SLIGHTLY OVER INTERIOR NE MA WHICH MEANS WE WILL ADD CENTRAL MIDDLESEX COUNTY MA TO ADVISORY AT THIS TIME. 12Z NAM/GFS ARE IN GENERAL AGREEMENT IN HANDLING OF POTENT SHORT WAVE AND ASSOCIATED SURFACE LOW DIVING SE FROM GREAT LAKES TONIGHT. WE ARE LEANING MORE TOWARD NAM FOR DETAILS GIVEN ITS BETTER RESOLUTION SINCE ELEVATION WILL PLAY A LARGE ROLE IN RAIN VS SNOW AS WELL AS SNOWFALL TOTALS. WE DO THINK NAM IS A BIT OVERDONE WITH ITS QPF OF 0.50 TO 0.75 INCH ACROSS MUCH OF NORTHERN MA AND SW NH...ESPECIALLY WHEN COMPARED WITH 09Z SREFS WHICH ONLY SUPPORT 0.25 TO 0.50 INCH. HOWEVER THEY DO AGREE THAT AXIS OF MAX QPF WILL BE ACROSS OUR NORTHERN ZONES...WITH LESSER AMOUNTS OF 0.10 TO 0.25 INCH S OF MASS PIKE. WE HAVE WARMED UP NICELY THIS AFTERNOON WITH ALL LOCATIONS WELL UP INTO THE 40S AND LOWER 50S. IT IS THIS LOW LEVEL WARMING THAT WILL BE KEY PLAYER IN HOW FAST WE SEE A CHANGEOVER FROM RAIN TO SNOW...SINCE ALOFT IT IS STILL FAIRLY COLD AND WILL EASILY SUPPORT SNOW AT ONSET. THIS IS A TYPICAL SPRING SNOWFALL EVENT WHERE HIGHER ELEVATIONS ARE FAVORED...BUT SINCE SNOW WILL BE FALLING AT NIGHT WE STAND TO SEE SOME ACCUMULATION AT LOWER ELEVATIONS AS WELL. IN ORDER TO SEE MORE WIDESPREAD ADVISORY TOTALS...WE WOULD LIKE TO SEE STRONGER LIFT ARRIVING AFTER MIDNIGHT...BUT SINCE IT IS COMING IN DURING FIRST PART OF NIGHT...THAT SHOULD LIMIT EXTENT OF 2 TO 4 INCH TOTALS. AS A RESULT...WE EXPECT LIGHT RAIN TO MOVE INTO SOUTHERN NEW ENGLAND THIS EVENING...POSSIBLY MORE OF A RAIN/SNOW MIX AT HIGHER ELEVATIONS... BEFORE CHANGING TO SNOW WITHIN A FEW HOURS OF ONSET. IN ADDITION TO WET BULB COOLING...WE ALSO HAVE STRONG LIFT ENTERING PICTURE AS A RESULT OF APPROACHING MID LEVEL SHORT WAVE...WHICH WILL ALSO ACT TO COOL DOWN COLUMN FAIRLY QUICKLY. THIS CHANGEOVER WILL TAKE PLACE BY 9 OR 10 PM ACROSS SW NH AND WESTERN/CENTRAL MA...BUT PROBABLY NOT UNTIL 11 PM OR MIDNIGHT FARTHER S AND E INTO NORTHERN CT...NORTHERN RI AND EASTERN MA...AND MORE LIKE 1 TO 2 AM NEAR S COAST. ALTHOUGH THIS SYSTEM IS PROGRESSIVE AND WILL EXIT REGION QUICKLY... THERE WILL BE A 3 TO 4 HOUR PERIOD WHERE EVERYTHING COMES TOGETHER TO PRODUCE DECENT SNOWFALL RATES...ESPECIALLY AT HIGHER ELEVATIONS WHERE SNOW WILL BE MORE PROLONGED AND OVER OUR NORTHERN ZONES WHERE CROSS SECTIONS INDICATE MAX SNOW GROWTH ZONE WILL BE. WHILE WE DO NOT SEE SNOWFALL TOTALS IN EXCESS OF 6 INCHES IN OUR HIGHER ELEVATION SITES...WE SHOULD BE ABLE TO GET WIDESPREAD 3 TO 5 INCH TOTALS FROM MONADNOCKS TO E SLOPES OF BERKSHIRES AND WORCESTER HILLS WITH 2 TO 4 INCHES ELSEWHERE ACROSS INTERIOR. FARTHER S INTO NORTHERN CT...NORTHERN RI AND INTERIOR EASTERN MA... WE THINK INITIAL LOW LEVEL WARMING WILL PLAY MORE OF A ROLE AND LIMIT SNOWFALL ACCUMULATIONS TO 1 TO 3 INCHES...MAINLY ON GRASS...SINCE RAIN/SNOW MIX SHOULD LAST A BIT LONGER AND BEST LIFT IS CENTERED IN WARMER AIR. SOME OF HIGHER ELEVATIONS OF HARTFORD...TOLLAND...WINDHAM AND PROVIDENCE COUNTIES COULD SEE AS MUCH AS 3 TO 4 INCHES LOCALLY...BUT WE DO NOT THINK THESE TOTALS WILL BE WIDESPREAD ENOUGH TO JUSTIFY ADVISORIES AT THIS TIME. SYSTEM WILL ALREADY BE OFFSHORE SUN MORNING...SO SNOW SHOULD BE OVER 4 TO 6 AM SUN. LOW LEVEL MOISTURE WILL HANG ON INTO MORNING PER CROSS SECTIONS...BEFORE DRYING SETS IN DURING MIDDAY AND AFTERNOON AND ALLOWS FOR SKIES TO CLEAR. TEMPERATURES SHOULD RECOVER NICELY SUN AFTERNOON...WELL INTO 40S IF NOT 50F AT A FEW SPOTS S OF MASS PIKE. WEAK HIGH PRESSURE BUILDS INTO REGION SUN NIGHT WITH ONLY PATCHY HIGH CLOUDS EXPECTED. LONG TERM /MONDAY THROUGH SATURDAY/... MEDIUM RANGE MODELS SHOWED PRETTY GOOD CONTINUITY THIS AFTERNOON... AT LEAST THE GFS SUITE AND BOTH THE GFS AND ECMWF ENSEMBLES. ALSO...BEYOND THURSDAY...MODELS SHOWING MORE SPREAD AMONG MANY OF THE SUITE MEMBERS...SO NOT A LOT OF CONFIDENCE WITH NEXT APPROACHING SYSTEM OUT OF THE MIDWEST LATE NEXT WEEK. USED MAINLY THE ENSEMBLES AND 00Z GFS FOR THIS PORTION OF THE FORECAST. HIGH PRESSURE WILL BUILD OFF THE SOUTH COAST MONDAY...HELPING SHIFT WINDS AROUND TO SOUTHWEST. WILL PROBABLY NOT FEEL THE FULL EFFECTS OF WARMER TEMPERATURES...BUT HIGHS IN THE 50S WILL FEEL NICE THOUGH REMAINING CHILLY ALONG THE SOUTH COAST. WARM FRONT DEVELOPS ACROSS THE GREAT LAKES DURING MONDAY...WITH AREA OF PRECIP QUICKLY PUSHING EAST. THERE WERE TIMING ISSUES THIS WARM FRONT AND A WEAK AREA OF LOW PRESSURE THAT MAY DEVELOP ALONG WITH IT FOR THE MONDAY NIGHT-TUESDAY TIMEFRAME. THE NAM/WRF WAS A GOOD 6-9 HOURS SLOWER THAN THE GFS RUN. HARD TO EXPLAIN...AS THE FORECASTED UPPER FLOW ON BOTH MODELS APPEARS IN LINE AS A WEAKENING UPPER SHORT WAVE RIDES OVER THE UPPER LEVEL RIDGE IN THE MIDWEST. DO NOTE THAT THE GFS IS A LITTLE FASTER AND STRONGER AS IT MOVES THROUGH. STILL A PRETTY FAST UPPER LEVEL FLOW...WHICH ALSO HELPS EXPLAIN THE TIMING DIFFERENCES. USED A BLEND OF THESE MODELS FOR TIMING THIS SYSTEM INTO THE REGION...AS THIS SYSTEM WILL BE ANOTHER FAST MOVER /SIMILAR TO TONIGHTS LOW/. LITTLE IF ANY COLD AIR TO WORK WITH...SO EXPECT THE PRECIP TO BE ALL RAIN AS IT APPROACHES LATE MONDAY...MOVING THROUGH TUESDAY MORNING. FORECASTED LOW MONDAY NIGHT COULD ACTUALLY RUN A FEW DEGREES ABOVE NORMAL WITH THIS LOW WITH SOME WARM AIR ADVECTION RIDING IN. ONCE THE LOW AND FRONT PUSH OFF THE COAST MIDDAY TUESDAY...CLOUDS WILL SLOWLY BREAK UP WITH DAYTIME HIGHS SOARING TO AROUND 60 DEGREES. THE OFFSHORE HIGH WILL BREAK DOWN AND HEAD EAST...WHILE ANOTHER HIGH BUILDS SOUTHEAST OUT OF CENTRAL CANADA BY WEDNESDAY MORNING. NOT MUCH WEATHER ASSOCIATED WITH THIS...BUT DO NOTE A SLIGHT COOLING TREND FOR THE MIDDLE OF NEXT WEEK. ANOTHER STRONGER LOW TAKES SHAPE OVER THE ROCKIES AROUND MIDWEEK. THE MODEL SUITE HAD A HANDLE ON THIS LOWS DEVELOPMENT...BUT HAVE A LOT OF ISSUES WITH THE TIMING OF THE SYSTEM AS IT TREKS ACROSS THE NORTHERN TIER FOR LATE NEXT WEEK. APPEARS THAT...FOR NOW...WILL CONTINUE WITH DRY WEATHER BUT A SLOW COOLING TREND AS THE CANADIAN HIGH TAKES HOLD. UPPER RIDGE BUILDS OVER THE GREAT LAKES AND MIDWEST...WHICH MAY HOLD THE WESTERN LOW AT BAY UNTIL LATE NEXT WEEK. CURRENT THINKING IS TO BRING IN A LOW CHANCE OF SHOWERS FOR FRIDAY NIGHT AND NEXT SATURDAY. AVIATION /18Z-18Z/... CONDITIONS LOWER TO MVFR IN CT VALLEY 00Z-02Z AND ON COASTAL PLAIN BY 04Z SUN AS PRECIPITATION SPREADS INTO REGION AHEAD OF CLIPPER LOW DIVING SE FROM GREAT LAKES. INITIALLY MOST LOCATIONS WILL HAVE RAIN...OR A RAIN/SNOW MIX ACROSS INTERIOR...BEFORE A TRANSITION TO SNOW 02Z-06Z AT ALL TERMINALS. EXCEPTION IS ON CAPE COD AND ISLANDS WHERE WE THINK IT WILL STAY AS A MIX OF RAIN AND SNOW. ALTHOUGH MVFR WILL DOMINATE TONIGHT WE DO EXPECT A PERIOD OF IFR OVERNIGHT...ESPECIALLY 03Z-07Z...BEFORE CONDITIONS SLOWLY IMPROVE AS PRECIPITATION MOVES OFFSHORE. HIGHER TERRAIN AIRPORT SUCH AS KORH SHOULD DROP TO LIFR...AS ARE MANY OF OUR SW NH AIRPORTS INCLUDING KMHT WHERE HEAVIEST SNOWFALL IS EXPECTED. WINDS NOT FORECAST TO BE AN ISSUE WITH THIS SYSTEM. LIGHT OR ONSHORE WINDS WILL BACK TO E/NE TONIGHT AND N/NE SUN...WITH SPEEDS AOB 10KT. MVFR TO START OFF SUN...BEFORE LIFTING TO VFR AROUND MIDDAY AS SKIES CLEAR OUT. OUTLOOK 18Z SUN TO 12Z MON...VFR WITH MOSTLY CLEAR SKIES AND LIGHT WINDS. MARINE... LOCAL SEA BREEZES WILL GIVE WAY TO E/NE WINDS TONIGHT...BUT AOB 10KT ON ALL WATERS. RAIN WILL MOVE INTO REGION THIS EVENING...AND WILL CHANGE TO SNOW LATER TONIGHT BEFORE ENDING BY DAYBREAK SUN. NE FLOW TRIES TO STRENGTHEN ON S COASTAL WATERS SUN MORNING AS LOW PRESSURE PASSES OFFSHORE...BUT WE EXPECT WINDS AND SEAS TO REMAIN BELOW SMALL CRAFT ADVISORY LEVELS. WEAK HIGH PRESSURE BUILDS OVER WATERS SUN AND SUN NIGHT. IN THE LONG TERM...HIGH PRESSURE IN CONTROL ON MONDAY...THOUGH SOUTHWEST WINDS WILL GUST UP TO 20 KTS LATE IN THE DAY AND MONDAY NIGHT AS WEAK LOW PRESSURE AND FRONT APPROACH. WINDS WILL SLOWLY SHIFT TO WEST AND NORTHWEST DURING TUESDAY AS LOW CLEARS THE COAST. HIGH PRESSURE TAKES OVER FROM CENTRAL CANADA FOR WEDNESDAY AND THURSDAY...WITH A NORTH TO NORTHWEST FLOW. WILL KEEP WIND GUSTS UP TO 20 KTS. BUT NOT IMPRESSIVE COLD AIR ADVECTION NOR GOOD PRESSURE GRADIENT AT THIS POINT SO WILL KEEP BELOW SMALL CRAFT...AT LEAST ON THE WINDS. WNA WAVEWATCH III MODEL TRIES TO BRING SEAS UP TO NEAR OR ABOVE 5 FEET ON THE FLOW AHEAD OF THE LOW AND FRONT MONDAY THROUGH TUESDAY NIGHT. WENT ABOUT 1 OR 2 FEET BELOW GUIDANCE. FELT THEY WERE OVERDONE WITH THE SOUTHWEST FLOW...BUT STILL CLOSE TO OR ABOVE SMALL CRAFT CRITERIA FOR A TIME...UPWARDS TO 6 FEET ON THE OUTER WATERS BOTH AHEAD AND BEHIND THE LOW AND FRONT. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...SNOW ADVISORY UNTIL 4 AM EDT SUNDAY FOR MAZ002>005-008>010-012- 026. NH...SNOW ADVISORY UNTIL 4 AM EDT SUNDAY FOR NHZ011-015. RI...NONE. MARINE...NONE. && $$ SHORT TERM...WTB
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
920 PM CDT SAT MAR 24 2007 .DISCUSSION UPDATE FOR TONIGHT... 920 PM AREAL FLOOD WATCH CANCELLED AS THREAT OF ANY HEAVY FLOOD PRODUCING RAINS NO LONGER EXISTS. FRONTAL BOUNDARY STILL RUNS FROM CENTRAL IA ACROSS NORTHERN IL INTO NORTHERN IN AT MID EVENING. HOWEVER...BAROCLINIC ZONE AND EFFECTIVE WARM FRONT CONTINUES LIFTING FURTHER NORTH...WITH BAND OF OVERUNNING RAIN NOW EXTENDING FROM NE SD ACROSS CENTRAL MN INTO W CENTRAL AND SOUTHERN WI. AIRCRAFT TEMPERATURE AND WIND PROFILES FROM ARRIVALS AND DEPARTURES AT ORD AND MDW SHOW THAT THE COOL LAYER ACROSS NORTHERN IL IS QUITE SHALLOW WITH SE WINDS VEERING TO SW BY 2-3K FT ALTITUDE. SATELLITE SHOWS A WEAK IMPULSE NNE FROM NORTHERN MO. SCT SHRA ACCOMPANED THIS FEATURE DURING THE FIRST PART OF THE EVENING BUT RADAR COMPOSITE NOW SHOWING A DECREASE IN ACTIVITY. WILL MAINTAIN A LOW CHC POP FOR SHRA ACROSS MAINLY N AND NE PORTION OF FA OVERNIGHT AS THE IMPULSE MAY STILL TRIGGER A FEW SHRA AS IT CONTINUES NEWRD. WITH MILD AND HIGER DEW POINTS ACROSS THE HAVE BUMPED UP TEMPS A BIT OFR OVERNIGHT ALSO. TRS .PREVIOUS DISCUSSION... 330 PM CDT A FLOOD WATCH WILL CONTINUE FOR THE ENTIRE AREA FOR SUNDAY AND SUNDAY NIGHT. THERE WILL BE CHANCE OF SHOWERS AND THUNDERSTORMS TONIGHT THROUGH MONDAY. THERE WILL BE FOG TONIGHT. THE UPPER AIR LOW WAS OVER ARIZONA THIS MORNING AND MOVED INTO SOUTHEAST COLORADO BY 1945 UTC. THIS IS SEEN ON THE WATER VAPOR LOOPS. THE PROFILER WIND AT 850 SHOWS THE 30 KNOTS OR GREATER OVER OKLAHOMA AND KANSAS. THIS IS A STRONGLY BAROCLINIC SYSTEM. THE GFS 500 MB FORECAST SHOWS HAS THE LOW OVER MINNESOTA BY 00 UTC MONDAY. THIS PUTS A JET STREAK OVER EASTERN IOWA AND SOUTHERN WISCONSIN. THE CHANCE OF THUNDERSTORMS AND SCATTERED THUNDERSTORMS TONIGHT AND SUNDAY ARE FROM A SURFACE WARM FRONT MOVING NORTH. THERE WILL BE CHANCE OF THUNDERSTORMS SUNDAY AFTERNOON AND LIKELY THUNDERSTORMS SUNDAY NIGHT. THAT IS WHEN WE EXPECT THE STRONGEST THUNDERSTORMS... POSSIBLY SEVERE. THE SUNDAY THUNDERSTORMS WILL BE A RESULT OF THE UPPER LOW AND JET STREAK. ANOTHER UPPER AIR WAVE WILL MOVE THROUGH THE MIDWEST TUESDAY. WE WILL HAVE A CHANCE OF THUNDERSTORMS IN THE FORECAST. THE TEMPERATURE WILL INCREASE SUNDAY THROUGH THE MIDDLE OF THE WEEK. MID TO UPPER 70S ARE FORECAST FOR HIGHS ON MONDAY. && .AVIATION... 654 PM 00Z TAFS...FIRST AND MAIN CONCERN THIS PERIOD WILL BE POTENTIAL FOR FOG AND LOW VIS. PREVAILING VIS GENERALLY 2-4SM ACROSS THE AREA WITH SOME LOCALLY DENSE FOG ALONG THE LAKE MICHIGAN SHORE. SETUP FOR FOG IS DIFFERENT THAN 24HRS AGO AND WHILE GUIDANCE DOES TAKE VIS/CIGS ON THE DECK AGAIN OVERNIGHT...LOCAL FOG PREDICTOR NOT INDICATING WIDESPREAD DENSE FOG FOR TONIGHT. NOT MUCH RAIN ACROSS THE AREA OVER THE TAF SITES OVER THE PAST 24 HRS AND TEMPS ARE 10 DEGREES WARMER THEN THIS TIME FRIDAY. SFC HIGH IS MOVING OFF TO THE EAST THIS EVENING AND EXPECT SE FLOW TO SET UP...THOUGH LIGHT. WHILE LOWER ATMOSPHERE REMAINS VERY MOIST THINK PREVAILING VIS LIKELY TO END UP IN THE 1SM RANGE WITH USUAL LOW SPOTS DROPPING TOWARD 1/2SM. LIKEWISE WITH SLIGHTLY BETTER VIS EXPECTED...CIGS SHOULD ALSO BE A LITTLE HIGHER. AS WINDS TURN MORE SOUTHERLY AROUND/AFTER SUNRISE SUNDAY...EXPECT FOG TO LIFT...LOW CLOUDS TO SCATTER OUT LEAVING A 3-5KFT STRATOCU/CU DECK FOR THE REMAINDER OF THE PERIOD. AS FOR WINDS...ESE WINDS UNDER 10KTS GRADUALLY TURN SE OVERNIGHT AND SPEEDS DIMINISH FURTHER TO 5KTS OR LESS. WINDS MAY BECOME LIGHT AND VRB BUT WILL MAINTAIN SE DIRECTION FOR NOW. ONCE WINDS SWING AROUND SOUTHERLY SUNDAY MORNING...SHOULD STEADILY INCREASE TO 10-15 KTS WITH GUSTS TO 20-22KTS...ESPECIALLY IN THE AFTERNOON. AS FOR PRECIP...MODELS SHOW LITTLE TO FOCUS PRECIP DEVELOPMENT THRU THE PERIOD. COULD BE A PASSING SHOWER TONIGHT...NOT WORTH MENTION AT THIS POINT. PRECIP FOCUS SHIFTS TO THE UPPER MIDWEST SUNDAY. SOME OF THIS ACTIVITY MAY REACH NORTHERN IL SUNDAY EVENING...WELL AFTER THE END OF THIS PERIOD. CMS && .LOT WATCHES/WARNINGS/ADVISORIES... .IL...NONE. .IN...NONE. .LM...NONE. && $$
AREA FORECAST DISCUSSION
NWS BALTIMORE MD/WASHINGTON DC
1101 AM EDT FRI MAR 23 2007 .SHORT TERM /THIS AFTN/... YDA...WHEN I SAW THE PTNL FOR A FNT TO HANG UP ALONG THE MASON-DIXON I KNEW TDA`S FCST WOULD HV HIGH "BUST PTNL"... SO MANY TIMES IN ERLY SPRING MDLS HV PROJECTED THE FNT TO SEEP SWD INTO THE CENTRAL CWA...ONLY TO HV IT HANG N...AND OUR FCST TEMPS ARE 10-15 DEGS TOO LOW. WE TOOK A SOMEWHAT OPTIMISTIC VIEW YDA...AND FCSTD MU60S FOR TDA. ATTM THE FNT IS HUNG ON THE PA SIDE OF THAT LN...AND TEMPS HV SOARED EVEN HIGHER S - CURRENTLY 74 AT THE OFFICE. UPPED THE THE TEMPS MANY LOCALES...XCPT ALONG THE BAY - NAK DROPPED 10 DEGS IN PAST HR DUE TO BAY BRZ. I`VE PARED BACK THE POPS THIS AFTN AS WELL...CUT DC FM LKLY TO CHC...AND IT MAY NOT BE UNTIL LATE THIS AFTN THAT THERE`S ANY CHC AT ALL. FNT STILL LOOKS TO SAG S THIS EVE. WOODY! && .PREV DISCUSSION... /ISSUED 345 AM EDT FRI MAR 23 2007/ SHORT TERM (TODAY THROUGH TONIGHT)... WATER VAPOR LOOP SHOWS A SHORT WAVE ACROSS NEW ENGLAND SHEARING SOUTHWEST INTO THE OHIO VALLEY...WHILE THE NEXT WAVE DROPS SOUTHEAST FROM THE UPPER MIDWEST TOWARD THE GREAT LAKES. AN UPPER LOW IS SPINNING NEAR SOUTHERN CALIFORNIA. ACARS 400-250MB WIND OBSERVATIONS REVEAL PHASING BETWEEN THE SOUTHERN STREAM AND NORTHERN STREAM IS TAKING PLACE ACROSS THE WESTERN GREAT LAKES. 03Z SURFACE ANALYSIS PLACED A COLD FRONT FROM A 989MB CYCLONE IN EASTERN QUEBEC SOUTHWEST THROUGH NEW ENGLAND...AND INTO THE MIDWEST WHERE IT IS STALLING. A SECONDARY STALLING COLD FRONT EXTENDED SOUTHWEST ACROSS SOUTHERN CANADA. A 1021MB ANTICYCLONE WAS LOCATED ACROSS THE LOWER GREAT LAKES. A TROUGH WAS NOTED IN THE LEE OF THE APPALACHIANS. SHORT WAVE MOVING INTO THE GREAT LAKES REGION IS PROMPTING A SECOND ROUND OF WARM ADVECTION ATOP TO FRONTAL BOUNDARY TO THE NORTH. THIS WILL PROVIDE A RAIN SHIELD WHICH IS TIMED TO ENTER THE NORTHWEST ZONES DURING THE FIRST FEW DAYLIGHT HOURS...THEN SPREAD EASTWARD ACROSS THE NORTHERN FORECAST AREA THROUGH THE MIDDAY...BEFORE DEVELOPING ACROSS CENTRAL VIRGINIA AROUND SUNSET (PER 21Z SHORT RANGE ENSEMBLES). THE 00Z LWX 6KM WRF-NMM MODEL SIMULATED RADAR REFLECTIVITY SHOWS A SIMILAR TREND. HAVE KEPT A MENTION OF THUNDER ACROSS CENTRAL VIRGINIA DEEPER WITHIN THE WARM SECTOR...WHERE 00Z NAM BUFKIT FORECAST SOUNDINGS EXHIBIT LOW CAPE. TONIGHT...EXPECT A GOOD COVERAGE OF LIGHT RAIN ACROSS THE REGION ESPECIALLY DURING THE EVENING AND EARLY OVERNIGHT HOURS...BEFORE THE NEXT ROUND OF WARM ADVECTION WANES. MEANWHILE...HEIGHT RISES TO THE NORTH WILL PROMOTE HIGH PRESSURE RIDGING DOWN THE APPALACHIANS...ENCOURAGING THE FRONTAL BOUNDARY TO SLIDE SOUTHWEST THROUGH THE FORECAST AREA. TEMPERATURES AND WINDS WILL BE DICTATED BY THE PROGRESS OF THE FRONTAL BOUNDARY. AVIATION... A SHIELD OF RAIN IS EXPECTED TO OVERSPREAD KMRB AND THE METRO HUBS BY EARLY AFTERNOON...LOWERING THE CEILING THROUGH THE VFR FLIGHT CATEGORY. A SIGNIFICANT AVIATION WEATHER CHANGE WILL OCCUR WITH THE PASSAGE OF A COLD FRONT SAGGING SOUTH FROM PENNSYLVANIA THIS EVENING...WHICH IS EXPECTED TO DROP CEILINGS TO NEAR THE IFR FLIGHT CATEGORY AND OFFER A WIND SHIFT FROM LIGHT AND VARIABLE...TO NORTHEAST. MARINE... 00Z ETA/GFS MOS AT THOMAS POINT INDICATE SUSTAINED WINDS UNDER 10KTS TODAY...AND AROUND 10KTS TONIGHT. 00Z NAM PROXIMITY FORECAST SOUNDINGS INDICATE ADDITIONAL WIND GUST POTENTIAL OF 15KTS TONIGHT (00Z GFS BUFKIT FORECAST SOUNDINGS DO NOT SHOW ADDITIONAL WIND GUST POTENTIAL). A MARG SCA EVENT STILL POSSIBLE SUN/MON BOTH AHEAD OF THE LOW PRES AND ESP BEYOND WHERE THE PRES GRAD INDUCED WIND WILL BE CONSIDERABLE. DUE TO LOW-END NATURE WILL CONTINUE TO MENTION STRAIGHT 15 KT FOR NOW AND CONTINUE TO MONITOR LTR TRENDS. TIDES... CHESAPEAKE BAY/TIDAL POTOMAC WATER LEVELS ARE CURRENTLY RUNNING AT ASTRONOMICAL PREDICTIONS. BOTH THE CHESAPEAKE BAY OPERATIONAL FORECAST SYSTEM AND NOAA EXTRATROPICAL STORM SURGE MODELS INDICATE WATER LEVELS WILL REMAIN AT OR FALL UP TO ONE FOOT BELOW ASTRONOMICAL PREDICTIONS THROUGH TODAY. THE LUNAR CYCLE IS WAXING TOWARD A QUARTER MOON (22% FULL). LONG TERM... SATURDAY THROUGH THURSDAY... ANOTHER LOW PRES WAVE DROPS FROM WESTERN PA INTO CTRL/NRN VA BY SAT AFTN...BRINGING RENEWED CHCS FOR RNFL. STILL SEEMS THAT BEST CHCS (LKLY POPS) WILL BE RELEGATED FROM KCBE TO BALTIMORE WHILE HOLDING AT CHC POPS ELSEWHERE INCLUDING THE IMMEDIATE DC AREA. ADDITIONAL ENERGY SAT EVNG WITH JET SUPPORT DROPPING INTO SRN PA. SEEMS THAT A LITTLE HVYR PRECIP WOULD BE POSSIBLE SAT EVNG ACROSS NRN MD INCLUDING THE KCBE-KFDK REGION DUE TO UPPER JET SUPPORT AND LOW LEVEL JET INDUCED HVYR PRECIP. HAVE UPDATED SAT NGT TO FEATURE LIKELY POPS IN THAT AREA. SOME ELEVATED INSTABILITY NOTED ON MDL SNDGS BUT WILL HOLD OFF MENTION OF TSTMS FOR NOW BUT WILL BE SOMETHING TO MONITOR. ANY PRECIP SUNDAY MORNING SHOULD END BY SHORTLY AFTER 12Z SO HAVE ELECTED TO KEEP SUN DRY STILL. HWVR...HAVE HAD TO INCREASE CLOUD COVER BASED ON LOW LEVEL NRLY FLOW SUN MRNG. BY SUN AFTN THOUGH WE ARE STILL EXPECTING SOME SUNSHINE. NO MAJOR CHGS NOTED IN PERIODS BEYOND SUN NGT WITH LOW CHCS FOR SHOWERS STILL INDICATED TUE-TUE NGT. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...NONE. && $$
AREA FORECAST DISCUSSION
NWS BALTIMORE MD/WASHINGTON DC
345 AM EDT FRI MAR 23 2007 .SHORT TERM (TODAY THROUGH TONIGHT)... WATER VAPOR LOOP SHOWS A SHORT WAVE ACROSS NEW ENGLAND SHEARING SOUTHWEST INTO THE OHIO VALLEY...WHILE THE NEXT WAVE DROPS SOUTHEAST FROM THE UPPER MIDWEST TOWARD THE GREAT LAKES. AN UPPER LOW IS SPINNING NEAR SOUTHERN CALIFORNIA. ACARS 400-250MB WIND OBSERVATIONS REVEAL PHASING BETWEEN THE SOUTHERN STREAM AND NORTHERN STREAM IS TAKING PLACE ACROSS THE WESTERN GREAT LAKES. 03Z SURFACE ANALYSIS PLACED A COLD FRONT FROM A 989MB CYCLONE IN EASTERN QUEBEC SOUTHWEST THROUGH NEW ENGLAND...AND INTO THE MIDWEST WHERE IT IS STALLING. A SECONDARY STALLING COLD FRONT EXTENDED SOUTHWEST ACROSS SOUTHERN CANADA. A 1021MB ANTICYCLONE WAS LOCATED ACROSS THE LOWER GREAT LAKES. A TROUGH WAS NOTED IN THE LEE OF THE APPALACHIANS. SHORT WAVE MOVING INTO THE GREAT LAKES REGION IS PROMPTING A SECOND ROUND OF WARM ADVECTION ATOP TO FRONTAL BOUNDARY TO THE NORTH. THIS WILL PROVIDE A RAIN SHIELD WHICH IS TIMED TO ENTER THE NORTHWEST ZONES DURING THE FIRST FEW DAYLIGHT HOURS...THEN SPREAD EASTWARD ACROSS THE NORTHERN FORECAST AREA THROUGH THE MIDDAY...BEFORE DEVELOPING ACROSS CENTRAL VIRGINIA AROUND SUNSET (PER 21Z SHORT RANGE ENSEMBLES). THE 00Z LWX 6KM WRF-NMM MODEL SIMULATED RADAR REFLECTIVITY SHOWS A SIMILAR TREND. HAVE KEPT A MENTION OF THUNDER ACROSS CENTRAL VIRGINIA DEEPER WITHIN THE WARM SECTOR...WHERE 00Z NAM BUFKIT FORECAST SOUNDINGS EXHIBIT LOW CAPE. TONIGHT...EXPECT A GOOD COVERAGE OF LIGHT RAIN ACROSS THE REGION ESPECIALLY DURING THE EVENING AND EARLY OVERNIGHT HOURS...BEFORE THE NEXT ROUND OF WARM ADVECTION WANES. MEANWHILE...HEIGHT RISES TO THE NORTH WILL PROMOTE HIGH PRESSURE RIDGING DOWN THE APPALACHIANS...ENCOURAGING THE FRONTAL BOUNDARY TO SLIDE SOUTHWEST THROUGH THE FORECAST AREA. TEMPERATURES AND WINDS WILL BE DICTATED BY THE PROGRESS OF THE FRONTAL BOUNDARY. && .AVIATION... A SHIELD OF RAIN IS EXPECTED TO OVERSPREAD KMRB AND THE METRO HUBS BY EARLY AFTERNOON...LOWERING THE CEILING THROUGH THE VFR FLIGHT CATEGORY. A SIGNIFICANT AVIATION WEATHER CHANGE WILL OCCUR WITH THE PASSAGE OF A COLD FRONT SAGGING SOUTH FROM PENNSYLVANIA THIS EVENING...WHICH IS EXPECTED TO DROP CEILINGS TO NEAR THE IFR FLIGHT CATEGORY AND OFFER A WIND SHIFT FROM LIGHT AND VARIABLE...TO NORTHEAST. && .MARINE... 00Z ETA/GFS MOS AT THOMAS POINT INDICATE SUSTAINED WINDS UNDER 10KTS TODAY...AND AROUND 10KTS TONIGHT. 00Z NAM PROXIMITY FORECAST SOUNDINGS INDICATE ADDITIONAL WIND GUST POTENTIAL OF 15KTS TONIGHT (00Z GFS BUFKIT FORECAST SOUNDINGS DO NOT SHOW ADDITIONAL WIND GUST POTENTIAL). A MARG SCA EVENT STILL POSSIBLE SUN/MON BOTH AHEAD OF THE LOW PRES AND ESP BEYOND WHERE THE PRES GRAD INDUCED WIND WILL BE CONSIDERABLE. DUE TO LOW-END NATURE WILL CONTINUE TO MENTION STRAIGHT 15 KT FOR NOW AND CONTINUE TO MONITOR LTR TRENDS. && .TIDES... CHESAPEAKE BAY/TIDAL POTOMAC WATER LEVELS ARE CURRENTLY RUNNING AT ASTRONOMICAL PREDICTIONS. BOTH THE CHESAPEAKE BAY OPERATIONAL FORECAST SYSTEM AND NOAA EXTRATROPICAL STORM SURGE MODELS INDICATE WATER LEVELS WILL REMAIN AT OR FALL UP TO ONE FOOT BELOW ASTRONOMICAL PREDICTIONS THROUGH TODAY. THE LUNAR CYCLE IS WAXING TOWARD A QUARTER MOON (22% FULL). && .LONG TERM... SATURDAY THROUGH THURSDAY... ANOTHER LOW PRES WAVE DROPS FROM WESTERN PA INTO CTRL/NRN VA BY SAT AFTN...BRINGING RENEWED CHCS FOR RNFL. STILL SEEMS THAT BEST CHCS (LKLY POPS) WILL BE RELEGATED FROM KCBE TO BALTIMORE WHILE HOLDING AT CHC POPS ELSEWHERE INCLUDING THE IMMEDIATE DC AREA. ADDITIONAL ENERGY SAT EVNG WITH JET SUPPORT DROPPING INTO SRN PA. SEEMS THAT A LITTLE HVYR PRECIP WOULD BE POSSIBLE SAT EVNG ACROSS NRN MD INCLUDING THE KCBE-KFDK REGION DUE TO UPPER JET SUPPORT AND LOW LEVEL JET INDUCED HVYR PRECIP. HAVE UPDATED SAT NGT TO FEATURE LIKELY POPS IN THAT AREA. SOME ELEVATED INSTABILITY NOTED ON MDL SNDGS BUT WILL HOLD OFF MENTION OF TSTMS FOR NOW BUT WILL BE SOMETHING TO MONITOR. ANY PRECIP SUNDAY MORNING SHOULD END BY SHORTLY AFTER 12Z SO HAVE ELECTED TO KEEP SUN DRY STILL. HWVR...HAVE HAD TO INCREASE CLOUD COVER BASED ON LOW LEVEL NRLY FLOW SUN MRNG. BY SUN AFTN THOUGH WE ARE STILL EXPECTING SOME SUNSHINE. NO MAJOR CHGS NOTED IN PERIODS BEYOND SUN NGT WITH LOW CHCS FOR SHOWERS STILL INDICATED TUE-TUE NGT. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...NONE. && $$ SHORT TERM/AVIATION/TIDES...ROGOWSKI LONG TERM...BROTHERTON MARINE...ROGOWSKI/BROTHERTON
AREA FORECAST DISCUSSION
NWS GAYLORD MI
1104 AM EDT FRI MAR 23 2007 .UPDATE...SFC ANALYSIS REVEALING BROAD HIGH PRESSURE ACROSS THE GREAT LAKES ALONG WITH A FAIRLY DRY AIRMASS (PWAT RUNNING AROUND 0.3 INCH OFF 12Z APX SOUNDING). AREA OF THICKER MID CLOUD ASSOCIATED WITH WEAK SHORT WAVE (PER WATER VAPOR IMAGERY) DRIFTING THROUGH THE NRN PORTION OF THE CWA THIS MORNING AND WILL BRING A PERIOD OF BKN SKIES PRIMARILY TO EASTERN UPPER MICHIGAN. OTHERWISE...ABUNDANT SUNSHINE IN STORE FOR THE REST OF THE CWA THIS AFTERNOON WITH TEMPERATURES JUST GETTING INTO THE 50S. LIGHT WINDS (925 MB WINDS UNDER 15 KNOTS) SHOULD RESULT IN LAKE BREEZE COMPONENT THIS AFTERNOON AND KEEP TEMPS A LITTLE COOLER FOR THE SHORELINE AREAS. OVERALL...ONLY MINOR TWEAKS MADE TO GOING FORECAST...AND UPDATE ALREADY SENT. HYDRO CONCERNS...USGS GAGE READINGS ON THE TOBACCO AND RIFLE RIVERS STILL GOING UP (ABOVE BANKFULL STAGE ON THE RIFLE RIVER NEAR STERLING). HOWEVER TREND HAS FLATTENED OUT THIS MORNING INDICATING THE RIVER LEVELS LIKELY NEARING PEAK. NONETHELESS...WILL TAKE AT LEAST ANOTHER DAY TO GET THE WATER THROUGH THE SYSTEM AND THE LEVELS BACK DOWN AGAIN. WILL MAKE SOME CALLS TO THE AREA AND CHECK FORECAST DATA...BUT ONGOING FLOOD WATCH AND WARNINGS WILL LIKELY NEED EXTENDING THROUGH TONIGHT AND PERHAPS SATURDAY. ADAM && .AVIATION...ISSUED AT 722 AM. VFR CONDITIONS SET TO PREVAIL ACROSS ALL TAF SITES OVER THE NEXT 24 HOURS AS HIGH PRESSURE SLOWLY TRAVERSES THE REGION. EARLY MORNING SCT-BKN 9KFT MID CLOUD DECK WILL GIVE WAY TO SOME SCATTERED CIRRUS BY MID MORNING. WITH LIGHT SYNOPTIC WIND REGIME UNDER HIGH PRESSURE...EXPECTING LAKE BREEZES TO KICK IN OFF LAKES MICHIGAN AND HURON DURING THE AFTERNOON. BIGGEST INFLUENCE EXPECTED AT TVC AND PLN WHERE LIGHT SOUTHEAST WINDS SHOULD QUICKLY VEER MORE WEST (PLN) TO NORTH (TVC) WITH PASSAGE OF LAKE FRONT. MSB && .DISCUSSION...ISSUED AT 257 AM. SPLIT FLOW IN PLACE ACROSS THE CONUS WITH THE GREAT LAKES BENEATH CONFLUENCE AXIS WHERE NORTHERN AND SOUTHERN BRANCHES MERGE BACK TOGETHER. NORTHERN BRANCH SHORT WAVE TROUGH CURRENTLY CROSSING THE NORTHERN ROCKIES EXPECTED TO CROSS THE REGION SATURDAY...MEANWHILE PERSISTENT SOUTHERN BRANCH UPPER LOW CURRENTLY CROSSING MEXICO FORECAST TO FILL AND LIFT NORTHEAST THIS WEEKEND...BUCKLING THE SOUTHERN BRANCH FLOW WHICH IN TURN WILL PROBABLY SEND THE EAST-WEST ORIENTED FRONTAL BOUNDARY OVER THE OHIO/MISSISSIPPI RIVER VALLEYS NORTHWARD. SO ATTENTION ON WEEKEND WEATHER POTENTIAL WILL BE THE MAIN FORECAST ISSUES THIS MORNING. TODAY/TONIGHT...MIDNIGHT SURFACE ANALYSIS SHOWS A SMALL BUBBLE OF HIGH PRESSURE OVER THE WESTERN LAKES...WITH MAIN FRONTAL BOUNDARY DRAPED ACROSS THE OHIO/MISSISSIPPI RIVER VALLEYS. CONVECTION FIRING ALONG THE FRONT BUT REMAINING MOSTLY SOUTH OF THE LOWER PENINSULA. WATER VAPOR IMAGERY SHOWS AN ELONGATED SHORT WAVE TROUGH CROSSING NORTHERN WI...AREA OF MID CLOUD OUT AHEAD OF THIS FEATURES ACROSS UPPER AND SPREADING INTO NORTHERN LOWER MI. 00Z RAOBS FROM APX/GRB WERE FAIRLY DRY (700MB DEW POINT DEPRESSIONS 14C). 03Z AIRCRAFT SOUNDING OUT OF PLN HAS MOISTENED A BIT IN THE MID LEVELS...BUT STILL DRY BELOW 700MB. AREA RADARS SHOWING SOME WEAK RETURNS CROSSING NORTHERN LAKE MICHIGAN...NO REPORTS OF ANYTHING REACHING THE GROUND WITH CEILING HEIGHTS IN THE 9-10K FOOT RANGE. SHORT WAVE TROUGH SHOULD ZIP THROUGH THE AREA EARLY THIS MORNING WITH LITTLE FANFARE OTHER THAN AN INCREASE IN MID CLOUD...WHICH SHOULD DIMINISH LATER THIS MORNING THOUGH THERE MAY BE SOME RESIDUAL CLOUD COVER HANGING ON ACROSS UPPER MI/STRAITS THROUGH THE DAY. SHOULD BE A GOOD DAY FOR LAKE BREEZE DEVELOPMENT AS WELL WITH WEAK GRADIENT IN PLACE...AND MILD AS WELL WITH AFTERNOON HIGHS RUNNING A GOOD 10 DEGREES ABOVE NORMAL. NORTHERN STREAM SHORT WAVE TROUGH EXPECTED TO APPROACH THE WESTERN LAKES BY SATURDAY MORNING. LOOKING FOR AN INCREASE IN MID/HIGH CLOUDS MAINLY ACROSS THE NORTHERN HALF OF THE FORECAST AREA TONIGHT IN ADVANCE OF THIS FEATURE. AS FOR THE CURRENT HYDROLOGIC ISSUES...PROBABLY ALL RIGHT TO DROP FLOOD WATCH FOR MANISTEE/WEXFORD COUNTIES...IF WE`RE GOING TO SEE FLOOD PROBLEMS FROM WEDNESDAY NIGHT`S RAINFALL EVENT PROBABLY WOULD HAVE SEEN THEM BY NOW. WILL KEEP THE FLOOD WATCH GOING FOR GLADWIN/ARENAC COUNTIES WHERE RIVER LEVELS ARE STILL TRENDING UPWARD...WITH FLOOD WARNING FOR ARENAC COUNTY ALONG RIFLE RIVER WHICH IS STILL RUNNING NEAR BANKFULL STAGE (9 FEET) THOUGH HYDROGRAPH SHOWING SIGNS OF RIVER NEARING CREST. SATURDAY...AFOREMENTIONED SHORT WAVE TROUGH WILL SWING ACROSS NORTHERN MI DURING THE DAY SATURDAY...WILL LIKELY BE EAST OF THE FORECAST AREA BY EVENING. SHOULD SEE MORE CLOUD COVER ACROSS NORTHERN MI SATURDAY AT LEAST THROUGH MID AFTERNOON...BUT WILL PROBABLY SEE SOME CLEARING BY LATE AFTERNOON IN WAKE OF THIS WAVE. WON`T RULE OUT SOME LIGHT PRECIP ACROSS EASTERN UPPER AND THE TIP OF THE MITT...LOWER LAYERS STILL FORECAST TO BE PRETTY DRY SO MAY JUST END UP WITH A GOOD DEAL OF VIRGA (LIKE EARLY THIS MORNING). DEEP LAYER RIDGING/ANTICYCLONIC FLOW THEN BUILD INTO THE WESTERN LAKES SATURDAY NIGHT IN THE WAKE OF THE NORTHERN STREAM WAVE...AND AHEAD OF SOUTHERN BRANCH LOW WHICH WILL BE CLIMBING UP THE WESTERN SIDE OF THIS RIDGE THROUGH THE HIGH PLAINS. LOOKING AT A QUIET SATURDAY NIGHT WITH RIDGING AND DRY AIR IN PLACE. SUNDAY THROUGH TUESDAY...FOR SUNDAY...WITH UPPER LEVEL PATTERN BECOMING MORE AMPLIFIED THIS WILL RE-ORIENT PERSISTENT FRONTAL BOUNDARY ACROSS THE OHIO/MISSISSIPPI VALLEYS FROM EAST-WEST TO NORTHWEST-SOUTHEAST AS WESTERN END OF THE FRONT GETS PUSHED NORTH ACROSS IA AND INTO MN/SOUTHERN WI. DRY AIR WILL STILL HANG ON MUCH OF THE DAY...BETTER MOIST INFLOW MAY NOT GET FOCUSED TOWARD LOWER MI UNTIL SUNDAY NIGHT...SO MUCH OF THE DAY SHOULD BE DRY AND MILD WITH PERHAPS JUST A LATE CHANCE FOR PRECIPITATION WEST OF M-37. WILL CARRY THUNDERSTORM CHANCES ALL AREAS FOR SUNDAY NIGHT WITH LOW LEVEL JET FOCUSED ON THE FORECAST AREA. MONDAY RAIN CHANCES STILL LOOK FINE THOUGH MAY END UP BEING MORE OF A MORNING ISSUE. TUESDAY FORECAST PROBABLY A BIT MORE UP IN THE AIR DEPENDING ON WHETHER FRONTAL BOUNDARY PUSHES THROUGH THE STATE OR GETS HUNG UP IF HEIGHT FALLS ARE NOT AS IMPRESSIVE AS INDICATED BY 22/12Z ECMWF OUTPUT. GIVEN THIS CONFLICT SEE NO NEED TO CHANGE CURRENT CHANCE POPS FOR TUESDAY (THOUGH WILL EXPAND TO COVER ALL AREAS). JPB && .APX WATCHES/WARNINGS/ADVISORIES...FLOOD WATCH...THROUGH THIS EVENING...MIZ041-042. FLOOD WARNING...THROUGH NOON...MIZ042. && $$
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
1100 AM EDT FRI MAR 23 2007 .UPDATE... MID CLOUDS CONTINUE TO LINGER LATE THIS MORNING OVER THE ERN FCST AREA...AND NEW CLOUD DEVELOPMENT IS OCCURRING OVER NCNTRL UPPER MI. CLOUDS ARE DEVELOPING IN AN AREA OF PERSISTENT ISENTROPIC ASCENT AS VIEWED ON 290K SFC (ROUGHLY 750-800MB) PER 12Z RUC. ASCENT SLACKENS DURING THE AFTN...SO CLOUDS SHOULD TEND TO THIN OUT SOME LATER IN THE AFTN. AS FOR TEMPS...12Z KINL/KGRB SOUNDINGS AND MORNING TAMDAR SOUNDING FROM KSAW SUPPORT RAISING HIGH TEMPS. KINL/KGRB SOUNDINGS YIELD HIGHS IN THE MID 50S TO AROUND 60F IF MIXED LAYER BUILDS TO 850MB WHILE KSAW SOUNDING SUPPORTS HIGHS IN THE LWR 50S. RAISED HIGHS TO THE LWR END OF THOSE VALUES GIVEN SOME CLOUD COVER. TEMPS WILL BE CONSIDERABLE COOLER NEAR LAKE MICHIGAN UNDER LIGHT SRLY FLOW...AND THE COOLING SHOULD EXTEND ACROSS ALL OF THE ERN FCST AREA. LAKE BREEZE SHOULD DEVELOP OFF LAKE SUPERIOR EXCEPT FOR AREAS E OF MARQUETTE AS SRLY FLOW SHOULD BE SUFFICIENT THRU THE AFTN TO PREVENT DEVELOPMENT THERE. && .PREV DISCUSSION (ISSUED AT 530 AM EDT)... MAIN FCST CONCERNS IN SHORT TERM ARE CLOUDS/TEMPS THEN FOCUS WILL BE ON TIMING OF NEXT CHC OF RAIN/THUNDERSTORMS FOR SUN AFTERNOON. WATER VAPOR IMAGERY AND RUC ANALYSIS SHOW ZONAL FLOW ACROSS THE NRN CONUS/SRN CANADA. ONE SHORTWAVE IS MOVING THROUGH THE UPR GREAT LAKES EARLY THIS MORNING WHILE ANOTHER IS UPSTREAM OVER SRN ALBERTA. SHORTWAVE MOVING THROUGH UPR GREAT LAKES PRODUCED A FEW FLURRIES THIS MORNING NORTH OF LAKE SUPERIOR IN AREA OF WEAK Q-VECT CONV AND ISENTROPIC ASCENT. MODEL SNDGS CONSISTENT IN SHOWING LINGERING MOISTURE AROUND 850 MB IN WAKE OF SHORTWAVE SO KEPT IN A BIT MORE CLOUD COVER TODAY IN ANTICIPATION OF STRATOCU DEVELOPING DURING THE DAY. MIXING TO 850-800MB ON FCST SOUNDINGS YIELDS HIGHS IN THE LOW/MID 50S OVER THE WRN INTERIOR. SRLY FLOW WILL KEEP TEMPS MUCH COOLER OVER THE ERN FCST AREA NEAR AND DOWNWIND OF LAKE MICHIGAN. LOCAL COOLING SHOULD ALSO OCCUR NEAR LAKE SUPERIOR OVER THE W AND NCNTRL AREAS MID/LATE AFTN WHERE BOUNDARY LAYER WINDS WILL BE LIGHTER. FROM MUNISING EWD...SRLY FLOW MAY STRONG ENOUGH 10-15 KT TO SUPRESS LAKE BREEZE DEVELOPMENT. NEXT SHORTWAVE FROM ALBERTA IS DUE TO MOVE INTO THE UPR GREAT LAKES LATE FRI NIGHT AND SAT. UPR DIV IN RRQ OF 100 KT 3H JET SHOULD PRODUCE SOME MID CLOUDS PER MODEL SNDGS BUT OTHERWISE MODEL SNDGS LOOK PRETTY DRY AT LOW LEVELS. WEAK PRES GRADIENTS WITH SFC HIGH OVERHEAD WILL ALLOW FOR LAKE BREEZES TO DEVELOP SAT OFF BOTH LAKES SUPERIOR AND MICHIGAN...KEEPING TEMPS COOLER (40S) ALONG LAKESHORE AREAS. MIXING TO AROUND 850 MB OVER THE WESTERN INTERIOR WILL ALLOW MAX TEMPS TO REACH NEAR TO MID 50S. SAT NIGHT...INFLUENCE OF SFC HIGH JUST TO THE NE OF LAKE SUPERIOR WILL ALLOW FOR LIGHT WIND AND GENERALLY CLEAR TO PARTLY CLOUDY SKIES. EXPECT LOWS TO REACH INTO THE 20S OVER THE INTERIOR...CLOSER TO COOLER GFS MOS GUIDANCE. MODELS STILL IN GOOD AGREEMENT SHOWING UPR LOW EJECTING OUT OF THE PLAINS AND INTO THE UPR GREAT LAKES SUN NIGHT INTO MON. AN INCREASING RIBBON OF MOISTURE/ISENTROPIC ASCENT ON THE 300K SFC... A 40KT H85 JET...AND PWATS AROUND AN INCH ARE MAIN TRIGGERS FOR SHOWERS LATE SUN INTO SUN NIGHT. NEG 850-500 MB THETA-E LAPSE RATES COULD ALSO RESULT IN THUNDER. BUMPED UP POPS TO LIKELY SUN NIGHT WITH ARRIVAL OF SFC WARM FRONT AND UPR TROUGH. DEPARTURE OF SHORTWAVE AND ASSOC SFC TROF/WARM FRONT SHOULD TAPER OFF RAIN CHCS BY MON AFTERNOON. && .MQT WATCHES/WARNINGS/ADVISORIES...NONE. && $$ ROLFSON (UPDATE) VOSS (PREV DISCUSSION)
AREA FORECAST DISCUSSION
NWS GAYLORD MI
722 AM EDT FRI MAR 23 2007 .AVIATION...VFR CONDITIONS SET TO PREVAIL ACROSS ALL TAF SITES OVER THE NEXT 24 HOURS AS HIGH PRESSURE SLOWLY TRAVERSES THE REGION. EARLY MORNING SCT-BKN 9KFT MID CLOUD DECK WILL GIVE WAY TO SOME SCATTERED CIRRUS BY MID MORNING. WITH LIGHT SYNOPTIC WIND REGIME UNDER HIGH PRESSURE...EXPECTING LAKE BREEZES TO KICK IN OFF LAKES MICHIGAN AND HURON DURING THE AFTERNOON. BIGGEST INFLUENCE EXPECTED AT TVC AND PLN WHERE LIGHT SOUTHEAST WINDS SHOULD QUICKLY VEER MORE WEST (PLN) TO NORTH (TVC) WITH PASSAGE OF LAKE FRONT. MSB && .DISCUSSION...ISSUED AT 257 AM. SPLIT FLOW IN PLACE ACROSS THE CONUS WITH THE GREAT LAKES BENEATH CONFLUENCE AXIS WHERE NORTHERN AND SOUTHERN BRANCHES MERGE BACK TOGETHER. NORTHERN BRANCH SHORT WAVE TROUGH CURRENTLY CROSSING THE NORTHERN ROCKIES EXPECTED TO CROSS THE REGION SATURDAY...MEANWHILE PERSISTENT SOUTHERN BRANCH UPPER LOW CURRENTLY CROSSING MEXICO FORECAST TO FILL AND LIFT NORTHEAST THIS WEEKEND...BUCKLING THE SOUTHERN BRANCH FLOW WHICH IN TURN WILL PROBABLY SEND THE EAST-WEST ORIENTED FRONTAL BOUNDARY OVER THE OHIO/MISSISSIPPI RIVER VALLEYS NORTHWARD. SO ATTENTION ON WEEKEND WEATHER POTENTIAL WILL BE THE MAIN FORECAST ISSUES THIS MORNING. TODAY/TONIGHT...MIDNIGHT SURFACE ANALYSIS SHOWS A SMALL BUBBLE OF HIGH PRESSURE OVER THE WESTERN LAKES...WITH MAIN FRONTAL BOUNDARY DRAPED ACROSS THE OHIO/MISSISSIPPI RIVER VALLEYS. CONVECTION FIRING ALONG THE FRONT BUT REMAINING MOSTLY SOUTH OF THE LOWER PENINSULA. WATER VAPOR IMAGERY SHOWS AN ELONGATED SHORT WAVE TROUGH CROSSING NORTHERN WI...AREA OF MID CLOUD OUT AHEAD OF THIS FEATURES ACROSS UPPER AND SPREADING INTO NORTHERN LOWER MI. 00Z RAOBS FROM APX/GRB WERE FAIRLY DRY (700MB DEW POINT DEPRESSIONS 14C). 03Z AIRCRAFT SOUNDING OUT OF PLN HAS MOISTENED A BIT IN THE MID LEVELS...BUT STILL DRY BELOW 700MB. AREA RADARS SHOWING SOME WEAK RETURNS CROSSING NORTHERN LAKE MICHIGAN...NO REPORTS OF ANYTHING REACHING THE GROUND WITH CEILING HEIGHTS IN THE 9-10K FOOT RANGE. SHORT WAVE TROUGH SHOULD ZIP THROUGH THE AREA EARLY THIS MORNING WITH LITTLE FANFARE OTHER THAN AN INCREASE IN MID CLOUD...WHICH SHOULD DIMINISH LATER THIS MORNING THOUGH THERE MAY BE SOME RESIDUAL CLOUD COVER HANGING ON ACROSS UPPER MI/STRAITS THROUGH THE DAY. SHOULD BE A GOOD DAY FOR LAKE BREEZE DEVELOPMENT AS WELL WITH WEAK GRADIENT IN PLACE...AND MILD AS WELL WITH AFTERNOON HIGHS RUNNING A GOOD 10 DEGREES ABOVE NORMAL. NORTHERN STREAM SHORT WAVE TROUGH EXPECTED TO APPROACH THE WESTERN LAKES BY SATURDAY MORNING. LOOKING FOR AN INCREASE IN MID/HIGH CLOUDS MAINLY ACROSS THE NORTHERN HALF OF THE FORECAST AREA TONIGHT IN ADVANCE OF THIS FEATURE. AS FOR THE CURRENT HYDROLOGIC ISSUES...PROBABLY ALL RIGHT TO DROP FLOOD WATCH FOR MANISTEE/WEXFORD COUNTIES...IF WE`RE GOING TO SEE FLOOD PROBLEMS FROM WEDNESDAY NIGHT`S RAINFALL EVENT PROBABLY WOULD HAVE SEEN THEM BY NOW. WILL KEEP THE FLOOD WATCH GOING FOR GLADWIN/ARENAC COUNTIES WHERE RIVER LEVELS ARE STILL TRENDING UPWARD...WITH FLOOD WARNING FOR ARENAC COUNTY ALONG RIFLE RIVER WHICH IS STILL RUNNING NEAR BANKFULL STAGE (9 FEET) THOUGH HYDROGRAPH SHOWING SIGNS OF RIVER NEARING CREST. SATURDAY...AFOREMENTIONED SHORT WAVE TROUGH WILL SWING ACROSS NORTHERN MI DURING THE DAY SATURDAY...WILL LIKELY BE EAST OF THE FORECAST AREA BY EVENING. SHOULD SEE MORE CLOUD COVER ACROSS NORTHERN MI SATURDAY AT LEAST THROUGH MID AFTERNOON...BUT WILL PROBABLY SEE SOME CLEARING BY LATE AFTERNOON IN WAKE OF THIS WAVE. WON`T RULE OUT SOME LIGHT PRECIP ACROSS EASTERN UPPER AND THE TIP OF THE MITT...LOWER LAYERS STILL FORECAST TO BE PRETTY DRY SO MAY JUST END UP WITH A GOOD DEAL OF VIRGA (LIKE EARLY THIS MORNING). DEEP LAYER RIDGING/ANTICYCLONIC FLOW THEN BUILD INTO THE WESTERN LAKES SATURDAY NIGHT IN THE WAKE OF THE NORTHERN STREAM WAVE...AND AHEAD OF SOUTHERN BRANCH LOW WHICH WILL BE CLIMBING UP THE WESTERN SIDE OF THIS RIDGE THROUGH THE HIGH PLAINS. LOOKING AT A QUIET SATURDAY NIGHT WITH RIDGING AND DRY AIR IN PLACE. SUNDAY THROUGH TUESDAY...FOR SUNDAY...WITH UPPER LEVEL PATTERN BECOMING MORE AMPLIFIED THIS WILL RE-ORIENT PERSISTENT FRONTAL BOUNDARY ACROSS THE OHIO/MISSISSIPPI VALLEYS FROM EAST-WEST TO NORTHWEST-SOUTHEAST AS WESTERN END OF THE FRONT GETS PUSHED NORTH ACROSS IA AND INTO MN/SOUTHERN WI. DRY AIR WILL STILL HANG ON MUCH OF THE DAY...BETTER MOIST INFLOW MAY NOT GET FOCUSED TOWARD LOWER MI UNTIL SUNDAY NIGHT...SO MUCH OF THE DAY SHOULD BE DRY AND MILD WITH PERHAPS JUST A LATE CHANCE FOR PRECIPITATION WEST OF M-37. WILL CARRY THUNDERSTORM CHANCES ALL AREAS FOR SUNDAY NIGHT WITH LOW LEVEL JET FOCUSED ON THE FORECAST AREA. MONDAY RAIN CHANCES STILL LOOK FINE THOUGH MAY END UP BEING MORE OF A MORNING ISSUE. TUESDAY FORECAST PROBABLY A BIT MORE UP IN THE AIR DEPENDING ON WHETHER FRONTAL BOUNDARY PUSHES THROUGH THE STATE OR GETS HUNG UP IF HEIGHT FALLS ARE NOT AS IMPRESSIVE AS INDICATED BY 22/12Z ECMWF OUTPUT. GIVEN THIS CONFLICT SEE NO NEED TO CHANGE CURRENT CHANCE POPS FOR TUESDAY (THOUGH WILL EXPAND TO COVER ALL AREAS). JPB && .APX WATCHES/WARNINGS/ADVISORIES...FLOOD WATCH...THROUGH THIS EVENING...MIZ041-042. && $$
AREA FORECAST DISCUSSION
NWS GAYLORD MI
257 AM EDT FRI MAR 23 2007 .DISCUSSION...SPLIT FLOW IN PLACE ACROSS THE CONUS WITH THE GREAT LAKES BENEATH CONFLUENCE AXIS WHERE NORTHERN AND SOUTHERN BRANCHES MERGE BACK TOGETHER. NORTHERN BRANCH SHORT WAVE TROUGH CURRENTLY CROSSING THE NORTHERN ROCKIES EXPECTED TO CROSS THE REGION SATURDAY...MEANWHILE PERSISTENT SOUTHERN BRANCH UPPER LOW CURRENTLY CROSSING MEXICO FORECAST TO FILL AND LIFT NORTHEAST THIS WEEKEND...BUCKLING THE SOUTHERN BRANCH FLOW WHICH IN TURN WILL PROBABLY SEND THE EAST-WEST ORIENTED FRONTAL BOUNDARY OVER THE OHIO/MISSISSIPPI RIVER VALLEYS NORTHWARD. SO ATTENTION ON WEEKEND WEATHER POTENTIAL WILL BE THE MAIN FORECAST ISSUES THIS MORNING. TODAY/TONIGHT...MIDNIGHT SURFACE ANALYSIS SHOWS A SMALL BUBBLE OF HIGH PRESSURE OVER THE WESTERN LAKES...WITH MAIN FRONTAL BOUNDARY DRAPED ACROSS THE OHIO/MISSISSIPPI RIVER VALLEYS. CONVECTION FIRING ALONG THE FRONT BUT REMAINING MOSTLY SOUTH OF THE LOWER PENINSULA. WATER VAPOR IMAGERY SHOWS AN ELONGATED SHORT WAVE TROUGH CROSSING NORTHERN WI...AREA OF MID CLOUD OUT AHEAD OF THIS FEATURES ACROSS UPPER AND SPREADING INTO NORTHERN LOWER MI. 00Z RAOBS FROM APX/GRB WERE FAIRLY DRY (700MB DEW POINT DEPRESSIONS 14C). 03Z AIRCRAFT SOUNDING OUT OF PLN HAS MOISTENED A BIT IN THE MID LEVELS...BUT STILL DRY BELOW 700MB. AREA RADARS SHOWING SOME WEAK RETURNS CROSSING NORTHERN LAKE MICHIGAN...NO REPORTS OF ANYTHING REACHING THE GROUND WITH CEILING HEIGHTS IN THE 9-10K FOOT RANGE. SHORT WAVE TROUGH SHOULD ZIP THROUGH THE AREA EARLY THIS MORNING WITH LITTLE FANFARE OTHER THAN AN INCREASE IN MID CLOUD...WHICH SHOULD DIMINISH LATER THIS MORNING THOUGH THERE MAY BE SOME RESIDUAL CLOUD COVER HANGING ON ACROSS UPPER MI/STRAITS THROUGH THE DAY. SHOULD BE A GOOD DAY FOR LAKE BREEZE DEVELOPMENT AS WELL WITH WEAK GRADIENT IN PLACE...AND MILD AS WELL WITH AFTERNOON HIGHS RUNNING A GOOD 10 DEGREES ABOVE NORMAL. NORTHERN STREAM SHORT WAVE TROUGH EXPECTED TO APPROACH THE WESTERN LAKES BY SATURDAY MORNING. LOOKING FOR AN INCREASE IN MID/HIGH CLOUDS MAINLY ACROSS THE NORTHERN HALF OF THE FORECAST AREA TONIGHT IN ADVANCE OF THIS FEATURE. AS FOR THE CURRENT HYDROLOGIC ISSUES...PROBABLY ALL RIGHT TO DROP FLOOD WATCH FOR MANISTEE/WEXFORD COUNTIES...IF WE`RE GOING TO SEE FLOOD PROBLEMS FROM WEDNESDAY NIGHT`S RAINFALL EVENT PROBABLY WOULD HAVE SEEN THEM BY NOW. WILL KEEP THE FLOOD WATCH GOING FOR GLADWIN/ARENAC COUNTIES WHERE RIVER LEVELS ARE STILL TRENDING UPWARD...WITH FLOOD WARNING FOR ARENAC COUNTY ALONG RIFLE RIVER WHICH IS STILL RUNNING NEAR BANKFULL STAGE (9 FEET) THOUGH HYDROGRAPH SHOWING SIGNS OF RIVER NEARING CREST. SATURDAY...AFOREMENTIONED SHORT WAVE TROUGH WILL SWING ACROSS NORTHERN MI DURING THE DAY SATURDAY...WILL LIKELY BE EAST OF THE FORECAST AREA BY EVENING. SHOULD SEE MORE CLOUD COVER ACROSS NORTHERN MI SATURDAY AT LEAST THROUGH MID AFTERNOON...BUT WILL PROBABLY SEE SOME CLEARING BY LATE AFTERNOON IN WAKE OF THIS WAVE. WON`T RULE OUT SOME LIGHT PRECIP ACROSS EASTERN UPPER AND THE TIP OF THE MITT...LOWER LAYERS STILL FORECAST TO BE PRETTY DRY SO MAY JUST END UP WITH A GOOD DEAL OF VIRGA (LIKE EARLY THIS MORNING). DEEP LAYER RIDGING/ANTICYCLONIC FLOW THEN BUILD INTO THE WESTERN LAKES SATURDAY NIGHT IN THE WAKE OF THE NORTHERN STREAM WAVE...AND AHEAD OF SOUTHERN BRANCH LOW WHICH WILL BE CLIMBING UP THE WESTERN SIDE OF THIS RIDGE THROUGH THE HIGH PLAINS. LOOKING AT A QUIET SATURDAY NIGHT WITH RIDGING AND DRY AIR IN PLACE. SUNDAY THROUGH TUESDAY...FOR SUNDAY...WITH UPPER LEVEL PATTERN BECOMING MORE AMPLIFIED THIS WILL RE-ORIENT PERSISTENT FRONTAL BOUNDARY ACROSS THE OHIO/MISSISSIPPI VALLEYS FROM EAST-WEST TO NORTHWEST-SOUTHEAST AS WESTERN END OF THE FRONT GETS PUSHED NORTH ACROSS IA AND INTO MN/SOUTHERN WI. DRY AIR WILL STILL HANG ON MUCH OF THE DAY...BETTER MOIST INFLOW MAY NOT GET FOCUSED TOWARD LOWER MI UNTIL SUNDAY NIGHT...SO MUCH OF THE DAY SHOULD BE DRY AND MILD WITH PERHAPS JUST A LATE CHANCE FOR PRECIPITATION WEST OF M-37. WILL CARRY THUNDERSTORM CHANCES ALL AREAS FOR SUNDAY NIGHT WITH LOW LEVEL JET FOCUSED ON THE FORECAST AREA. MONDAY RAIN CHANCES STILL LOOK FINE THOUGH MAY END UP BEING MORE OF A MORNING ISSUE. TUESDAY FORECAST PROBABLY A BIT MORE UP IN THE AIR DEPENDING ON WHETHER FRONTAL BOUNDARY PUSHES THROUGH THE STATE OR GETS HUNG UP IF HEIGHT FALLS ARE NOT AS IMPRESSIVE AS INDICATED BY 22/12Z ECMWF OUTPUT. GIVEN THIS CONFLICT SEE NO NEED TO CHANGE CURRENT CHANCE POPS FOR TUESDAY (THOUGH WILL EXPAND TO COVER ALL AREAS). JPB && .APX WATCHES/WARNINGS/ADVISORIES...FLOOD WATCH...THROUGH THIS EVENING...MIZ041-042. && $$
AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA
NWS SIOUX FALLS SD
900 PM CDT SAT MAR 24 2007 .DISCUSSION... TRICKY FCST FOR THE REST OF TONIGHT...IN TRYING TO FIGURE OUT HOW THE REST OF THE EVENT WILL EVOLVE. 00Z RAOBS SHOW THE H5 LOW CENTER JUST NE OF DENVER...WITH DECENT LOW LVL JET PER THE H85 LEVEL STREAMING NWD AHEAD OF IT THRU CENTRAL AND WRN KS...ERN NEB AND INTO THE ERN HALF OF THE FSD FA. LOW LVL WAA IS IN NO SHORT SUPPLY TONIGHT. SO THEREFORE WE KEEP GETTING THESE SMALL SHOWERS TO KEEP REDEVELOPING IN ERN NEB...THEN LIFTING NEWD INTO NW IA AND PARTS OF SW MN ALONG THE STRONGEST MSTR TRANSPORT VECTORS. SO FAR...ACTIVITY HAS BEEN WELL BLO SVR LIMITS IN THIS CWA WITH LIMITED INSTABILITY. THE 00Z LBF SNDG DOES SHOW STRONG INSTABILITY IN THE LOWEST 3 KM...WITH OAX ALSO SHOWING GOOD INSTABILITY IN THE LOWEST 2 KM...THEN IT BECOMES CONDITIONALLY UNSTABLE BETWEEN 2 KM TO 3 KM. WERE MONITORING THE CLUSTER OF STORMS WHICH DEVELOPED IN WRN KS EARLY THIS EVENING...AND HAVE NOW PROGRESSED INTO CENTRAL NEB MOVG NEWD. THE PROBLEM IS...THE DYNAMICS WITH THIS SYSTEM IS NOT OVERLY IMPRESSIVE...AS WELL AS STRONG INSTABILITY IN OUR FA. WHAT IS IMPRESSIVE IS THE WIND SHEAR HOWEVER...VERY STRONG ALONG THE WRMFNT WHICH IS LIFTING NWD THRU THE FSD FA TONIGHT. 0-1KM AND 0-3KM ARE OUT OF SIGHT NEAR THE WRMFNT. IN ADDITION...WE DO HAVE AN INVERTED TROF JUTTING NWD FM A SFC LOW WHICH IS IN SW NEB...INTO CENTRAL SD. SO OBVIOUSLY...MOST OF THE SFC AND NEAR SFC DYNAMICS ARE ASSOCIATED WITH THE WRMFNT WHERE THE SFC VORT IS VERY STRONG. BUT THE MID AND UPPER LEVELS REMAIN WEAK. IN THE LATEST GRIDS WHICH I WL UPLOAD SOON...HAVE TRIED TO TIME THE COMPLEX INTO THE WRN AND SRN PTNS OF THE FSD FA FIRST BY LATE EVENING...THEN LIFTING IT NWD AND NEWD AS THE OVERNIGHT PROGRESSES. WITH THE WHOLE UPPER LOW LIFTING NEWD...IT IS QUITE POSSIBLE THAT SOME FORM OF THIS COMPLEX WL EVENTUALLY HIT EVEN OUR N CENTRAL PART OF OUR FA LATE TONIGHT...AND MODELS FOR A COUPLE OF DAYS NOW HAVE SHOWN THE GREATEST INSTABILITY IN OUR FA BETWEEN 03Z AND 09Z TONIGHT. BUT AS SAID EARLIER...INSTABILITY IS NOT ALL THAT TREMENDOUS IN THIS FA. PROBABLY GREATEST SVR THREAT WL BE OVER THE FAR SRN FA TONIGHT IN THE FORM OF HAIL TO QUARTER SIZE. WIND THREAT WL LIKELY DECREASE AS THE NIGHT PROGRESSES WITH THE THERMAL INVERSION STRENGHTENING. && .PREV DISCUSSION... THE BIG QUESTION FOR TONIGHT BECOMES WHAT WILL HAPPEN AFTER WARM ADVECTION BAND LIFTS NORTH OF INTERSTATE 90 AROUND 00Z. DRY SLOT AND UPPER LEVEL COLD POOL MOVE INTO CENTRAL NEBRASKA THIS EVENING AND THE NEAR SFC TO 925MB CAPE VALUES INCREASE TO ABOUT 1000-1500 J/KG WITH LITTLE CAPPING. AN 18Z ACARS SOUNDING FROM OMAHA SUGGESTED THAT SOMETHING AROUND THE MID 70S WOULD BE NEEDED TO BREAK THE CAP...AND WITH LNK POPPING UP TO 77 AT 19Z...IT LOOKS LIKE THERE SHOULD BE ENOUGH HEAT TO SUPPORT SOME SFC BASED CONVECTION WHEN UPPER LEVEL SUPPORT ENTERS THE AREA. THE FORECAST SOUNDING FROM OFK SEEMS REASONABLE WITH 22Z TEMPS IN THE UPPER 60S...SO WILL ADD A THREAT FOR SEVERE INTO THE SOUTH. MOST THREATENING SEVERE PARAMETERS APPEAR TO BE THE 0-1KM CAPE AND BULK SHEAR WHICH ARE AROUND 100-200 J/KG AND 30 KNOTS RESPECTIVELY FROM ABOUT YKN TO SUX...WHICH MAY HINT AT THE POTENTIAL FOR A MINI-SUPERCELL CASE. UNFORTUNATELY THE FBY PROFILER APPEARS TO BE OUT AND NLG DIED AROUND 03Z...SO WILL BE TOUGH TO MONITOR THE DEVELOPING WIND FIELD. NOT ACCEPTABLE DURING A POTENTIALLY TORNADIC SITUATION. WILL BE CANCELLING FLOOD WATCH FOR COUNTIES INTO NW IOWA WITH UPCOMING FORECAST PACKAGE. COULD SEE ANOTHER ONE HALF INCH OF PRECIPITATION INTO THIS AREA...WHICH WOULD NOT POSE FLOODING PROBLEMS. HIGHEST QPFS TONIGHT ARE EXPECTED WEST INTO CNTRL SD. OTHERWISE...WENT ABOUT 2 TO 4 DEGREES WARMER THAN GUIDANCE FOR LOWS TONIGHT...LOW TO MID 50S...WITH DECENT FLOW AND 925MB TEMPS IN THE TEENS C. RECORD WARM LOWS FOR THE AREA WILL PROBABLY BE BROKEN. THOSE RECORDS FOR THE MORNING OF THE 25TH ARE 47 AT BOTH SIOUX FALLS AND HURON AND 55 AT SIOUX CITY. UPPER WAVE TO EXIT EWRD ACROSS MN TOMORROW EVENING...BRINGING AN END TO THREAT OF SHOWERS AND THUNDERSTORMS AS LARGE SCALE SUBSIDENCE SETS IN. WESTERLY WINDS WILL ADVECT IN DRIER AIR TOMORROW NIGHT... HOWEVER MODELS ARE NOT NEARLY AS AGGRESSIVE WITH DRIER COLDER AIR BEHIND UPPER WAVE...AND ARE NOW MUCH WARMER ON MONDAY. LIGHT SRLY WINDS...AMPLE SUNSHINE...AND WARM AIR ALOFT...WILL HAVE NO PROBLEM REACHING THE 70S...EVEN A FEW LOWER 80S POSSIBLE SOUTH AND WEST ON MONDAY. ALSO A SLIGHT CHANCE FOR THUNDERSTORM DEVELOPMENT MONDAY EVENING WITH A -6 LIFTED INDEX AND 1500 J/KG CAPE NEAR SUX...BASED OFF THE NAM. NAM BRINGS S/WV INTO NW BY LATE AFTERNOON...WHICH WOULD BREAK THE WEAK CAP. GFS HOWEVER...IS MUCH MORE STABLE WITH S/WV FARTHER SOUTH...THUS ONLY SLIGHT CHANCE OF THUNDERSTORMS. FLOW TURNING MORE SRLY ON MONDAY...ADVECTING LOW TO MID 50 DEW POINTS INTO MUCH OF THE AREA BY TUE...EVEN THOUGH GUIDANCE SUGGESTS DEW POINTS ONLY IN THE LOW TO MID 40S. THIS BEING THE CASE...WENT ABOVE GUIDANCE LOWS TUE AND WED NIGHT. NEXT GOOD CHANCE OF PRECIPITATION WILL BE LATE WED INTO WED NIGHT AS THE NEXT UPPER LOW TRACKS INTO THE NRN PLNS. SHOULD BE A VERY DYNAMIC SYSTEM WITH A STRONG COLD FRONT...SO COULD BE DEALING WITH SEVERE WEATHER WITH THIS SYSTEM. && .AVIATION... SFC WRMFNT SEEMS TO HAVE ARCED TO LOWER MO VLY FROM KYKN TO KSUX...MARKED BY WIND SHIFT TO MORE SLY AND DROP IN DWPT...EXTENDING BACK TO LOW PRESSURE IN SWRN NEBRASKA. EVEN IN WARM SECTOR...SURGE OF LOW LVL MOISTURE SEEN PUSHING RAPIDLY NWRD THRU ERN PORTIONS OF KS/NEBRASKA. EXPECT THAT STRATUS WL REDEVELOP ALG/N OF WARM FRONT THRU THE EVNG...BUT ALSO EXPAND FROM S INTO KSUX/KFSD EVEN AS FRONT LIFTS N...AS LOW LVL FLOW BACKS TOWARD A SE DIRECTION SOMEWHAT IN RESPONSE TO THE STRONG DYNAMICAL SYSTEM TO W. ORGANIZED CONVECTIVE AREA LKLY TO SWEEP UP THRU TWB316 BY 04-05Z...WITH MORE SCT ACTIVITY BACK TOWARD KSUX. ANALYSIS OF OAX RAOB LEAVES ANY SIGNIFICANT DEEP INSTABILITY UNDISCOVERED...BUT A TALL VERY THIN CAPE OF 100. MUCH COOLER MID LVL TMPS TOWARD N...SO INCREASE IN MOISTURE WL MAKE FOR INCREASED INSTABILITY HEADING NWRD. MAINLY MVFR AND SOME IFR CIGS WL BREAK UP FROM THE SW AS UPR WAVE/SFC LOW PUSHES EWRD TOWARD THE I29 CORRIDOR BY 18Z...WITH INFLUX OF DRYING W/SW FLOW. && .FSD WATCHES/WARNINGS/ADVISORIES... IA...NONE. MN...NONE. NE...NONE. SD...NONE. && $$ MJF/CHAPMAN
AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA
NWS SIOUX FALLS SD
310 PM CDT SAT MAR 24 2007 .DISCUSSION... THE BIG QUESTION FOR TONIGHT BECOMES WHAT WILL HAPPEN AFTER WARM ADVECTION BAND LIFTS NORTH OF INTERSTATE 90 AROUND 00Z. DRY SLOT AND UPPER LEVEL COLD POOL MOVE INTO CENTRAL NEBRASKA THIS EVENING AND THE NEAR SFC TO 925MB CAPE VALUES INCREASE TO ABOUT 1000-1500 J/KG WITH LITTLE CAPPING. AN 18Z ACARS SOUNDING FROM OMAHA SUGGESTED THAT SOMETHING AROUND THE MID 70S WOULD BE NEEDED TO BREAK THE CAP...AND WITH LNK POPPING UP TO 77 AT 19Z...IT LOOKS LIKE THERE SHOULD BE ENOUGH HEAT TO SUPPORT SOME SFC BASED CONVECTION WHEN UPPER LEVEL SUPPORT ENTERS THE AREA. THE FORECAST SOUNDING FROM OFK SEEMS REASONABLE WITH 22Z TEMPS IN THE UPPER 60S...SO WILL ADD A THREAT FOR SEVERE INTO THE SOUTH. MOST THREATENING SEVERE PARAMETERS APPEAR TO BE THE 0-1KM CAPE AND BULK SHEAR WHICH ARE AROUND 100-200 J/KG AND 30 KNOTS RESPECTIVELY FROM ABOUT YKN TO SUX...WHICH MAY HINT AT THE POTENTIAL FOR A MINI-SUPERCELL CASE. UNFORTUNATELY THE FBY PROFILER APPEARS TO BE OUT AND NLG DIED AROUND 03Z...SO WILL BE TOUGH TO MONITOR THE DEVELOPING WIND FIELD. NOT ACCEPTABLE DURING A POTENTIALLY TORNADIC SITUATION. WILL BE CANCELLING FLOOD WATCH FOR COUNTIES INTO NW IOWA WITH UPCOMING FORECAST PACKAGE. COULD SEE ANOTHER ONE HALF INCH OF PRECIPITATION INTO THIS AREA...WHICH WOULD NOT POSE FLOODING PROBLEMS. HIGHEST QPFS TONIGHT ARE EXPECTED WEST INTO CNTRL SD. OTHERWISE...WENT ABOUT 2 TO 4 DEGREES WARMER THAN GUIDANCE FOR LOWS TONIGHT...LOW TO MID 50S...WITH DECENT FLOW AND 925MB TEMPS IN THE TEENS C. RECORD WARM LOWS FOR THE AREA WILL PROBABLY BE BROKEN. THOSE RECORDS FOR THE MORNING OF THE 25TH ARE 47 AT BOTH SIOUX FALLS AND HURON AND 55 AT SIOUX CITY. UPPER WAVE TO EXIT EWRD ACROSS MN TOMORROW EVENING...BRINGING AN END TO THREAT OF SHOWERS AND THUNDERSTORMS AS LARGE SCALE SUBSIDENCE SETS IN. WESTERLY WINDS WILL ADVECT IN DRIER AIR TOMORROW NIGHT... HOWEVER MODELS ARE NOT NEARLY AS AGGRESSIVE WITH DRIER COLDER AIR BEHIND UPPER WAVE...AND ARE NOW MUCH WARMER ON MONDAY. LIGHT SRLY WINDS...AMPLE SUNSHINE...AND WARM AIR ALOFT...WILL HAVE NO PROBLEM REACHING THE 70S...EVEN A FEW LOWER 80S POSSIBLE SOUTH AND WEST ON MONDAY. ALSO A SLIGHT CHANCE FOR THUNDERSTORM DEVELOPMENT MONDAY EVENING WITH A -6 LIFTED INDEX AND 1500 J/KG CAPE NEAR SUX...BASED OFF THE NAM. NAM BRINGS S/WV INTO NW BY LATE AFTERNOON...WHICH WOULD BREAK THE WEAK CAP. GFS HOWEVER...IS MUCH MORE STABLE WITH S/WV FARTHER SOUTH...THUS ONLY SLIGHT CHANCE OF THUNDERSTORMS. FLOW TURNING MORE SRLY ON MONDAY...ADVECTING LOW TO MID 50 DEW POINTS INTO MUCH OF THE AREA BY TUE...EVEN THOUGH GUIDANCE SUGGESTS DEW POINTS ONLY IN THE LOW TO MID 40S. THIS BEING THE CASE...WENT ABOVE GUIDANCE LOWS TUE AND WED NIGHT. NEXT GOOD CHANCE OF PRECIPITATION WILL BE LATE WED INTO WED NIGHT AS THE NEXT UPPER LOW TRACKS INTO THE NRN PLNS. SHOULD BE A VERY DYNAMIC SYSTEM WITH A STRONG COLD FRONT...SO COULD BE DEALING WITH SEVERE WEATHER WITH THIS SYSTEM. && .AVIATION... STRONG WARM FRONT ACROSS NEBRASKA WILL KEEP SFC FLOW AT AN EAST OR SOUTHEAST DIRECTION. UPPER LEVEL SUPPORT SHOULD MOVE INTO NEBRASKA LATE THIS AFTERNOON...ALLOWING FOR ADDITIONAL THUNDERSTORM DEVELOPMENT THERE...WHICH SHOULD MOVE ACROSS THE SUX AND FSD TAF SITES FROM ABOUT 01Z THROUGH 04Z. OTHERWISE...THE HON TAF SHOULD SEE SOME IFR AND POTENTIALLY SOME LIFR CONDITIONS TONIGHT AND ESPECIALLY AFTER 08Z. SIMILAR THOUGHTS FOR FSD. && .FSD WATCHES/WARNINGS/ADVISORIES... IA...NONE. MN...NONE. NE...NONE. SD...NONE. && $$ LIEBL/08