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000
FXUS61 KRNK 201327
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
927 AM EDT MON MAY 20 2013

.SYNOPSIS...
LOW PRESSURE ALOFT WILL MOVE ACROSS THE REGION TODAY AND TONIGHT. A
LARGE LOW PRESSURE SYSTEM WILL TRACK FROM THE CENTRAL PLAINS INTO
THE GREAT LAKES BY THURSDAY. THIS SYSTEM WILL PUSH A COLD FRONT
THROUGH THE AREA THURSDAY...FOLLOWED BY HIGH PRESSURE ON FRIDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
THIS MORNING 8AM/12Z RNK SOUNDING SHOWED PLENTY OF MOISTURE UP TO
600 MB WITH A PWAT AT 1.27 INCHES. WFCX 88D LOOP DISPLAYED STORMS
IN THE WEST DROPPING SOUTH...WHILE STORMS IN THE EAST PIVOTING
NORTHEAST. MOVEMENT OF THE CONVECTION BEING SHAPED BY THE
SHORTWAVE ALONG THE VA/NC BORDER SLICING EASTWARD. WITH SLOW
MOVING OR TRAINING THUNDERSTORMS THIS AFTERNOON WE WILL HAVE TO
WATCH FOR LOCAL FLOODING PROBLEMS OVER A SATURDATED GROUND.
ADJUSTED POPS ACCORDING LATEST RADAR TRENDS. MODIFIED TEMPERATURES
AND DEWPOINTS ACCORDING TO LATEST OBS AND MODEL TRENDS. LOOKING AT
THE RNK WRFARW AND NAM FOCUS FOR THUNDERSTORMS THIS MORNING WILL
OCCUR MAINLY ALONG AND WEST OF I77 THEN THIS AFTERNOON MODELS
SHIFTS MAIN DEVELOPEMENT IN OUR EAST. MORE ADJUSTMENTS LATER.


AS OF 435 AM EDT MONDAY...

BASED ON WATER VAPOR LOOP AND LATEST RADAR TRENDS...CENTER OF
SHORT WAVE WAS NEAR THE VA/TN/NC BORDER. A MAJORITY OF THE MODELS
HAVE THIS FEATURE JUST SOUTHEAST OF THE FORECAST AREA AT 00Z/8PM
TONIGHT. STARTING OUT WITH A LOT OF CLOUDS TODAY BUT AS WINDS
ALOFT SHIFT TO THE SOUTHWEST THEN WEST SHOULD GETS SOME BREAKS IN
THE CLOUDS...ESPECIALLY EAST OF THE BLUE RIDGE AS THE UPSLOPE
WEAKENS.

RUC GUIDANCE SUGGESTED A BAND OF SHOWERS AND THUNDERSTORMS WILL
DEVELOP ALONG THE BLUE RIDGE AND FOOTHILLS THIS AFTERNOON. THE 00Z
LOCAL WRF FORECAST A CLUSTER OF STORMS OVER THE SOUTHWEST COUNTY
WARNING AREA. DIRECTION STORMS WILL MOVE WILL DEPEND ON WHERE THE
SHORT WAVE TRACKS. STORMS THIS AFTERNOON AND EVENING WEST OF THE
BLUE RIDGE SHOULD MOVE TO THE SOUTH. ALL MODELS HAD THE BULK OF
PRECIPITATION OUT OF THE FORECAST AREA BY MIDNIGHT. PROBABILITY OF
PRECIPITATION LOWER FROM WEST TO EAST OVERNIGHT TO ACCOUNT FOR
THIS TREND. 850 MB WINDS BECOME SOUTHWEST THEN WEST
TODAY...BRINING WARMER AIR INTO THE REGION AND ENHANCING THE LIFT
WITH THAT WARM AIR ADVECTION.

ANY BREAKS IN THE CLOUDS WILL RESULT IN A QUICK WARMUP TODAY.
LEANED TOWARD MET GUIDANCE FOR MAXIMUM TEMPERATURES. LOWS TONIGHT
WILL REMAIN MILD.

&&

.SHORT TERM /TUESDAY THROUGH THURSDAY NIGHT/...
AS OF 346 AM EDT SATURDAY...

SUFFICIENT INSTABILITY FOR AIRMASS THUNDERSTORMS BOTH TUESDAY AND
WEDNESDAY. A PATCH OF DRIER AIR AT H7 BOTH OF THESE DAYS SHOULD
LIMIT COVERAGE...BUT FOR THE STORMS THAT DO PUNCH THROUGH THIS
LAYER...THEY COULD BE STRONG. H85 TEMPS A FEW DEGREES COOLER ON
WEDNESDAY...BUT NEAR +17C ON TUESDAY SUGGESTS HIGHS NEAR 90F IN THE
CITIES...SO WENT WITH THE WARMER MAV MOS TEMPS. SEEMS AS THOUGH NAM
MODEL SOUNDINGS HAVE LESS INSTABILITY BECAUSE THE HIGH TEMPS ARE
MUCH COOLER THAN H85 ADJUSTMENTS WOULD SUGGEST. STRONGER STORMS ALSO
POSSIBLE THURSDAY AS COLD FRONT ARRIVES...BUT THERE MAY BE ENOUGH
CLOUDS AHEAD OF THE BOUNDARY THURSDAY TO LIMIT MORE NUMEROUS AND
STRONGEST STORMS TO THE VA/NC PIEDMONT. LATEST 0Z ECMWF DELIVERING A
GOOD CHUNK OF COOLER AIR BY 12Z FRIDAY ACROSS SE WEST VA WITH H85
TEMPS SLIPPING TO +5C...WHICH IS MUCH COLDER THAN THE REST OF HE
MODEL SUITE.

&&

.LONG TERM /FRIDAY THROUGH SUNDAY/...
AS OF 150 PM EDT SUNDAY...

AN UPPER LEVEL CLOSED LOW WILL SPIN AROUND THE UPPER MISSISSIPPI
VALLEY THROUGH AT LEAST FRIDAY. IN ADVANCE OF THIS SYSTEM...PLENTY
OF MOISTURE WILL ADVECT NORTHWARD INTO OUR REGION.

PIECES OF ENERGY WILL SPIRAL EASTWARD FROM THE MAIN SYSTEM AND
COMBINE WITH DAYTIME HEATING TO CREATE SHOWERS AND THUNDERSTORMS.
HPC CONTINUES TO FAVOR A SLOWER TIMING OF THE COLD FRONT. THE FRONT
IS EXPECTED TO EXIT OUR AREA FRIDAY EVENING INTO FRIDAY NIGHT. ECMWF
REMAINS FASTER THAN GFS WITH TIMING OF COLD FRONT. DO NOT BELIEVE
THE SFC LOW THAT DEVELOPS OFF THE SOUTHEAST ON GFS. HIGH PRESSURE
WILL RIDGE SOUTH FROM THE GREAT LAKES ON SATURDAY AND SLIDE EAST ON
SUNDAY.

COOLING TREND EXPECT FOR FRIDAY AND SATURDAY. HIGHS ON FRIDAY
WILL RANGE FROM AROUND 70 DEGREES IN THE WEST TO NEAR 80 DEGREES
IN THE SOUTHEAST. SATURDAY HIGHS ONLY REACH THE MID 60S ACROSS
THE MOUNTAINS TO THE LOWER 70S ACROSS THE PIEDMONT. HIGHS FOR
SUNDAY WILL WARM A COUPLE OF DEGREES FROM THE MID 60S IN THE WEST
TO THE MID 70S IN THE EAST.

&&

.AVIATION /13Z MONDAY THROUGH FRIDAY/...
AS OF 730 AM EDT MONDAY...

LOCAL RADAR SHOWED SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS
JUST WEST OF BLF EARLY THIS MORNING. THIS PRECIPITATION WAS MOVING
SSE AND MAY REMAIN JUST WEST OF THE BLF AIRPORT THROUGH 14Z/10AM.
EXPECT IFR TO LIFR STRATUS AND FOG TO GRADUALLY LIFT THIS MORNING.
CONDITIONS WILL BE SLOW TO IMPROVE...HOWEVER SURFACE AND LOW LEVEL
WINDS WILL GRADUALLY BECOME SOUTHWEST TODAY...ENDING THE UPSLOPE
FLOW. EXPECT TAF SITES (BLF/ROA/LWB/BCB/DAN/LYH) TO BE MVFR BY
1PM.

A SHORT WAVE SLOWLY CROSSING THE AREA TODAY WILL AGAIN TRIGGER
SHOWERS AND THUNDERSTORMS. ANY OF THE STRONGER STORMS WILL HAVE
VERY HEAVY RAIN...AS WELL AS IFR TO MVFR CEILINGS AND VISIBILITIES.

THE REGION STAYS IN A WARM...MOIST AIRMASS THROUGH THURSDAY.
PATCHY FOG WITH MVFR VISIBILITIES IS LIKELY EACH NIGHT AND EACH
AFTERNOON AND EVENING THERE WILL BE SCATTERED THUNDERSTORMS.

NEXT FRONT APPROACHES ON THURSDAY WITH MORE SHOWERS/STORMS
DEVELOPING. HIGH PRESSURE AND BETTER FLYING CONDITIONS ARE
EXPECTED ON FRIDAY BEHIND THE FRONT.

&&

.RNK WATCHES/WARNINGS/ADVISORIES...
VA...NONE.
NC...NONE.
WV...NONE.

&&

$$
SYNOPSIS...AMS
NEAR TERM...AMS/KK
SHORT TERM...KM
LONG TERM...KK
AVIATION...AMS/PM