Official-casts
Posted by JAC on 5/23/2011, 7:16 am
| SHORT RANGE FORECAST DISCUSSION NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD 432 AM EDT MON MAY 23 2011 VALID 12Z MON MAY 23 2011 - 12Z WED MAY 25 2011 ...THREAT FOR HEAVY RAIN CONTINUES ACROSS THE MIDDLE MISSISSIPPI VALLEY... ...SEVERE THUNDERSTORMS ARE POSSIBLE FROM THE SOUTHERN PLAINS TO THE NORTHERN MID-ATLANTIC STATES... A MAJORITY OF THE COUNTRY WILL CONTINUE TO EXPERIENCE UNSETTLED WEATHER OVER THE NEXT FEW DAYS. IN THE EAST...AN AREA OF LOW PRESSURE WILL QUICKLY MOVE NORTHEASTWARD INTO EASTERN CANADA...BRINGING WIDESPREAD SHOWERS TO MUCH OF THE GREAT LAKES REGION AND INTERIOR NORTHEAST MONDAY AFTERNOON AND INTO TUESDAY MORNING. THE NORTHERN PORTION OF A TRAILING FRONT WILL SLOWLY PUSH EASTWARD INTO THE NORTHEAST MONDAY NIGHT AND TUESDAY...RESULTING IN CONTINUED SHOWERS AND A FEW THUNDERSTORMS DURING THE DAY TUESDAY. A FEW OF THESE STORMS COULD BE STRONG. TO THE SOUTH...WARM...MOIST GULF AIR WILL ENCOUNTER THE SOUTHERN PORTION OF THE TRAILING FRONT...CREATING A RISK FOR SEVERE THUNDERSTORMS FROM THE SOUTHERN PLAINS TO THE OHIO RIVER VALLEY ON MONDAY. THESE STORMS MAY BE ACCOMPANIED BY HEAVY DOWNPOURS...HIGH WINDS...HAIL...AND TORNADOES. THIS PORTION OF THE FRONT WILL REMAIN QUASI-STATIONARY OVER THE SOUTHERN PLAINS...MIDDLE MISSISSIPPI VALLEY...AND OHIO VALLEY...MEANING MANY OF THE SAME PLACES MAY HAVE TO DEAL WITH ANOTHER ROUND OF SEVERE WEATHER ON TUESDAY. ELSEWHERE...INSTABILITY CAUSED BY DAYTIME HEATING WILL TRIGGER A FEW SCATTERED SHOWERS AND THUNDERSTORMS FROM THE SOUTHERN APPALACHIANS INTO THE MID-ATLANTIC ON MONDAY. MEANWHILE...A CLOSED UPPER-LOW WILL CONTINUE TO SPIN OVER THE NORTHWEST AS THE FORECAST PERIOD BEGINS. THE ENERGY WILL TRIGGER SHOWERS AND THUNDERSTORMS ACROSS THE NORTHERN AND CENTRAL ROCKIES ON MONDAY AND TUESDAY. ENERGY FROM THIS LOW WILL MAKE ITS WAY ACROSS THE ROCKIES AND INTO THE PLAINS BY WEDNESDAY MORNING. THIS WILL AIDE IN DEVELOPING A STRONG SURFACE CYCLONE OVER THE CENTRAL PLAINS ON WEDNESDAY AND BRINING MORE UNSETTLED WEATHER TO THE REGION IN FORM OF HEAVY RAIN AND SEVERE THUNDERSTORMS. UPSTREAM...ANOTHER STRONG DISTURBANCE WILL APPROACH THE PACIFIC NORTHWEST. PRECIPITATION COULD BEGIN TO MOVE INTO THE COASTAL REGIONS OF OREGON AND WASHINGTON OVERNIGHT TUESDAY AND INTO THE EARLY MORNING HOURS ON WEDNESDAY. GERHARDT  AY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0809 PM CDT SUN MAY 22 2011 VALID 230100Z - 231200Z ...THERE IS A MDT RISK OF SVR TSTMS ACROSS FAR WEST CENTRAL ILLINOIS...PORTIONS OF CENTRAL AND SOUTHERN MISSOURI...NORTHEAST OKLAHOMA...AND NORTHWEST ARKANSAS... ...THERE IS A SLGT RISK OF SVR TSTMS FROM THE GREAT LAKES/OH VALLEY/CENTRAL APPALACHIANS REGION SWWD INTO THE SRN PLAINS... ...UPPER GREAT LAKES REGION SWWD TO SWRN TX... AN EXTENSIVE/BROKEN BAND OF THUNDERSTORMS -- INCLUDING LARGE/EMBEDDED SUPERCELLS -- EXTENDS FROM UPPER MI/WI SWWD INTO THE TRANSPECOS REGION OF TX AND ADJACENT NRN MEXICO. NRN PORTIONS OF THE BAND ARE ASSOCIATED WITH THE SURFACE COLD FRONT...WITH THE MORE SRN PORTIONS OF THE BAND INTO OK/TX MORE TIED TO A DRYLINE. WIDESPREAD STORMS HAVE OVERTURNED THE AIRMASS IN MANY LOCALES...EFFECTIVELY REDUCING WHAT WAS STRONG INSTABILITY -- PARTICULARLY ACROSS MANY AREAS FROM NRN IL NWD. HOWEVER...STRONG INSTABILITY /MIXED-LAYER CAPE RANGING FROM 2000 TO 4000 J/KG/ REMAINS FROM CENTRAL MO SWWD TO SWRN TX...AND ANOTHER RESERVOIR OF MIXED-LAYER CAPE UP TO 2000 J/KG REMAINS ACROSS LOWER MI. GIVEN FAVORABLE SHEAR FOR SUPERCELLS ACROSS THE MAJORITY OF THIS AREA...WILL MAINTAIN SLIGHT RISK FROM LOWER MI SWWD TO SWRN TX...AND WILL MAINTAIN MODERATE RISK FROM THE STL /ST. LOUIS MO/ VICINITY SWWD INT NWRN AR/NERN OK. DAMAGING WINDS AND LARGE HAIL WILL REMAIN THE PRIMARY SEVERE THREATS...THOUGH ISOLATED TORNADOES REMAIN POSSIBLE THIS EVENING -- PARTICULARLY ACROSS THE MODERATE RISK AREA. ...OH AND TN VALLEYS INTO THE CENTRAL APPALACHIANS... TWO CLUSTERS OF STRONG/LOCALLY SEVERE STORMS CONTINUE ATTM -- ONE ACROSS NERN INDIANA/NWRN OH/SRN LOWER MI AND THE OTHER CROSSING THE CENTRAL APPALACHIANS REGION IN CONJUNCTION WITH AN UPPER SHORT-WAVE TROUGH. WHILE THESE STORMS SHOULD WEAKEN SLOWLY WITH TIME...WILL MAINTAIN SLIGHT RISK ACROSS THIS AREA FOR MARGINAL HAIL/DAMAGING WIND POTENTIAL. FINALLY...ALL HIGH-RES MODELS HINT THAT STORMS NOW ONGOING ACROSS MO MAY EVOLVE INTO AN MCS AND SHIFT ACROSS MO/NRN AR AND THE MID MS VALLEY INTO THE OH AND TN VALLEYS OVERNIGHT. WHILE LESS UNSTABLE AIR IS EVIDENT ACROSS MUCH OF KY AND TN IN THE WAKE OF EARLIER STORMS NOW IN THE CENTRAL APPALACHIANS...HAIL AND ISOLATED DAMAGING WINDS WILL BE POSSIBLE -- MAINLY FROM SRN INDIANA/WRN KY/WRN TN WWD. ..GOSS.. 05/23/2011  DAY 2 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 1240 AM CDT MON MAY 23 2011 VALID 241200Z - 251200Z ...THERE IS A MDT RISK OF SVR TSTMS LATE TUE AFTN INTO TUE NIGHT ACROSS CENTRAL AND EASTERN OKLAHOMA...MUCH OF CENTRAL AND EASTERN KANSAS...PARTS OF SOUTHWEST MISSOURI...NORTHWEST ARKANSAS AND NORTH CENTRAL TEXAS... ...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE MODERATE RISK AREA ACROSS MUCH OF THE CENTRAL PLAINS INTO THE MIDDLE MISSISSIPPI VALLEY...EASTWARD THROUGH PARTS OF THE LOWER OHIO AND TENNESSEE VALLEYS...AND NORTHEASTWARD THROUGH THE NORTHERN MID ATLANTIC COAST STATES AND HUDSON VALLEY... ...AN OUTBREAK OF SEVERE THUNDERSTORMS AND TORNADOES IS POSSIBLE LATE TUESDAY AFTERNOON AND EVENING... ...SYNOPSIS... MODELS INDICATE THAT THE LARGE-SCALE TROUGH...NOW DEVELOPING INTO THE WESTERN U.S...GRADUALLY SPLITS...WITH A SIGNIFICANT SOUTHERN PORTION SLOWLY LIFTING EAST NORTHEASTWARD OUT OF THE SOUTHERN PLATEAU BY EARLY TUESDAY...AS ANOTHER LARGE AND STRONG IMPULSE APPROACHES THE PACIFIC COAST. THE LEAD TROUGH...WITH AT LEAST A COUPLE OF SIGNIFICANT EMBEDDED SMALLER SCALE IMPULSES...IS PROGGED TO EVOLVE INTO A CLOSED LOW AS IT MIGRATES ACROSS THE SOUTHERN ROCKIES INTO THE CENTRAL PLAINS LATER TUESDAY AND TUESDAY NIGHT. ASSOCIATED FORCING FOR UPWARD VERTICAL MOTION APPEARS LIKELY TO CONTRIBUTE TO FURTHER DEEPENING OF A SURFACE CYCLONE OVER THE SOUTH CENTRAL PLAINS. THIS IS EXPECTED TO BE ACCOMPANIED BY A STRENGTHENING SOUTHERLY LOW-LEVEL JET IN EXCESS OF 50 KT AT 850 MB BY EARLY TUESDAY EVENING...FROM NORTH CENTRAL TEXAS INTO EASTERN KANSAS...AS A CYCLONIC AND GENERALLY WESTERLY 70 KT 500 MB JET STREAK NOSES INTO AND THROUGH THE SOUTHERN PLAINS RED RIVER VALLEY REGION. AT THE SAME TIME...A LARGE COLD UPPER VORTEX WITH SEVERAL STRONG EMBEDDED SHORT WAVE IMPULSES WILL LINGER OVER MUCH OF EASTERN CANADA. AN ASSOCIATED SIGNIFICANT COLD FRONT APPEARS LIKELY TO ADVANCE SOUTHEAST OF THE GREAT LAKES THROUGH MUCH OF THE NORTHEAST...AS ANOTHER IMPULSE...PERHAPS CONVECTIVELY ENHANCED...WITHIN THE SOUTHERN BRANCH OF THE SPLIT UPPER FLOW...LIFTS OUT OF THE OHIO VALLEY THROUGH SOUTHERN NEW ENGLAND BY 12Z WEDNESDAY. GIVEN THE CONTINUING PRESENCE OF A SEASONABLY MOIST BOUNDARY LAYER AIR MASS IN THE WARM SECTOR OF THE PLAINS CYCLONE...AND ALONG AND AHEAD OF THE EASTERN COLD FRONT...DESTABILIZATION PROBABLY WILL BECOME SUFFICIENT TO SUPPORT CONSIDERABLE STRONG/SEVERE STORM DEVELOPMENT DURING THIS PERIOD. ASIDE FROM SOME SEA BREEZE STORMS IN THE SOUTHEAST...THIS WILL MOSTLY REMAIN WEST AND NORTH OF PERSISTENT SUBTROPICAL RIDGING CENTERED JUST EAST OF THE SOUTH ATLANTIC COAST. ...CENTRAL/SOUTHERN PLAINS... LINGERING VARIABILITY AMONG THE MODELS AND ENSEMBLES CONCERNING THE TIMING AND TRACK OF THE TROUGH EMERGING FROM THE SOUTHWEST CONTINUES TO COMPLICATE THE FORECAST. BUT IT APPEARS THAT THIS WILL ONLY IMPACT THE EXACT PLACEMENT OF THE HIGHEST SEVERE PROBABILITIES...AS THE EVOLVING LARGE-SCALE PATTERN SEEMS SUPPORTIVE OF A FAIRLY CLASSIC SEVERE WEATHER OUTBREAK. AND ENOUGH COMMON GROUND APPEARS TO EXIST TO JUSTIFY AN UPGRADE TO MODERATE RISK SEVERE PROBABILITIES ACROSS MUCH OF CENTRAL/EASTERN KANSAS AND OKLAHOMA...PORTIONS OF NORTH CENTRAL TEXAS...NORTHWEST ARKANSAS AND SOUTHWEST MISSOURI. SURFACE DEW POINTS AROUND 70F ARE PROGGED IN THE WARM SECTOR OF THE DEEPENING CYCLONE...ALONG AND EAST OF A SHARPENING DRY LINE DURING THE LATE AFTERNOON HOURS...WHEN PEAK AFTERNOON HEATING AND STEEPENING LAPSE RATES ASSOCIATED WITH MID-LEVEL COOLING PROBABLY WILL CONTRIBUTE TO MIXED LAYER CAPE OF 2000-4000 J/KG. AS THE MID-LEVEL JET NOSES INTO THE RED RIVER VALLEY...THE DRY LINE IS EXPECTED TO BECOME THE FOCUS FOR THE PRIMARY STORM DEVELOPMENT AS IT SURGES NORTHEASTWARD OUT OF SOUTH CENTRAL KANSAS...AND EASTWARD OUT OF CENTRAL OKLAHOMA...THROUGH MUCH OF EASTERN KANSAS AND OKLAHOMA BY LATE EVENING. GIVEN THE ANTICIPATED WIND PROFILES...EXHIBITING STRONG DEEP LAYER SHEAR AND LARGE CLOCKWISE CURVED LOW-LEVEL HODOGRAPHS...THE ENVIRONMENT IS EXPECTED TO BECOME CONDUCIVE TO LONG-LIVED SUPERCELLS CAPABLE OF PRODUCING VERY LARGE HAIL AND STRONG TORNADOES. THIS THREAT MAY CONTINUE THROUGH MUCH OF THE EVENING...PERHAPS INTO THE 06-09Z TIME FRAME...GRADUALLY SPREADING TOWARD THE LOWER MISSOURI VALLEY AND OZARKS...BEFORE DIMINISHING IN THE PRESENCE OF A MORE STABLE OR STABILIZING BOUNDARY LAYER. ...NORTHERN MID ATLANTIC STATES INTO THE LOWER HUDSON VALLEY... WEAK TO MODERATE DESTABILIZATION ALONG AND AHEAD OF THE SOUTHEASTWARD ADVANCING COLD FRONT...AND WITHIN THE PRE-FRONTAL LEE SURFACE TROUGH...IS EXPECTED TO PROVIDE THE FOCUS FOR VIGOROUS CONVECTIVE DEVELOPMENT WITH THE APPROACHING UPPER IMPULSE TUESDAY AFTERNOON. MODELS ARE A BIT MORE UNCLEAR CONCERNING THE STRENGTH OF THE VERTICAL SHEAR...BUT IT SHOULD BE ENOUGH TO SUPPORT POTENTIAL FOR ORGANIZED STORM CLUSTERS...AND ISOLATED SUPERCELLS MAY NOT BE OUT OF THE QUESTION. THIS COULD IMPACT MUCH OF THE URBAN CORRIDOR...FROM WASHINGTON D.C./BALTIMORE TO NEW YORK CITY...BEFORE CONVECTION DIMINISHING/SPREADS OFFSHORE WITH UPPER FORCING BY TUESDAY EVENING. ..KERR.. 05/23/2011 |
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Looks like a rough ride this week - severe weather is back - JAC, 5/23/2011, 7:04 am
- Strong gravity waves over OK with moderate STP. - JAC, 5/23/2011, 3:45 pm
- MO Under-the-Gun again for Tuesday - JAC, 5/23/2011, 7:22 am
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