308
FXUS64 KJAN 181540 AAA
AFDJAN
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE JACKSON MS
1040 AM CDT SAT MAY 18 2013
UPDATE
WARM AND HUMID CONDITIONS WILL INCREASE THIS AFTERNOON AS H5 RIDGE
AXIS TO THE WEST BUILDS INTO THE REGION. TEMPERATURES WILL WARM INTO
THE MID/UPPER 80S. REGIONAL 12Z SOUNDINGS INDICATE THE STRONG CAPPING
IN THE REGION. THIS CAPPING WILL WEAKEN LATER THIS AFTERNOON AND AID
IN THE SLIGHT CLEARING OF CLOUDS THROUGH THE REGION. THERE IS
CURRENTLY A BOUNDARY IN NORTHEAST MISSISSIPPI FROM THE PREVIOUS
CONVECTION LAST NIGHT. THIS BOUNDARY AND UPPER S/WV...AS INDICATED
PER WATER VAPOR IMAGERY...MAY SERVE AS A FOCUS FOR ACTIVITY LATER
THIS AFTERNOON TO EVENING. IT IS DEFINITELY POSSIBLE THAT THE
ACTIVITY COULD STAY JUST TO THE NORTH OF THE REGION. HOWEVER...SEEMED
PRUDENT TO INTRODUCE SOME SLIGHT CHANCE POPS UNTIL 6Z DUE TO THE
CLOSE VICINITY OF THIS BOUNDARY. SOME HI-RES/GLOBAL MODELS ARE
INDICATING SOME SHOWERS AND THUNDERSTORMS DEVELOPING IN THE NORTHEAST
FROM THE GOLDEN TRIANGLE AND CONTINUING TO MOVE SOUTHEAST. THE
ENVIRONMENT WILL BE FAVORABLE FOR THUNDERSTORM DEVELOPMENT WITH
700-500MB LAPSE RATES AROUND 7-8.5 DEG C/KM...MLCAPES AROUND
2000-3000 J/KG AND SHOWALTERS AROUND -5 TO -7. ANY STORMS THAT
DEVELOP COULD BE STRONG AND PRODUCE SMALL HAIL AND WIND GUSTS UP TO
40 TO 50MPH. ONLY OTHER CHANGES WERE TO SLIGHTLY BUMP UP HIGHS/HOURLY
TEMP GRIDS DUE TO THE AREA WARMING QUICKER. SLIGHTLY ADJUSTED SKY
COVER GRIDS. REST OF THE FORECAST IS ON TRACK. /DC/
AVIATION
LOW LEVEL MOISTURE INFLUX IS STILL BRINGING MVFR
CEILINGS TO PORTIONS OF THE REGION AT MID MORNING...BUT THESE
RESTRICTIONS SHOULD IMPROVE IN ALL AREAS BEFORE NOON.
OTHERWISE...EXPECT FEW TO SCATTERED CU AROUND THIS AFTERNOON WITH
BASES FROM 3 TO 5 KFT. THE ONLY POTENTIAL TROUBLESPOT COULD BE
AROUND THE GOLDEN TRIANGLE (CBM/GTR) WHERE AT LEAST ISOLATED AFT/EVE
STORMS WILL REMAIN A POSSIBILITY DUE TO THE VICINITY OF A STATIONARY
FRONT. IF ANY STORMS MANAGE TO AFFECT THOSE SITES THEY COULD OF
COURSE BRING TEMPORARY MVFR TO IFR CONDITIONS...AS WELL AS THE
POTENTIAL FOR GUSTY WINDS AND LOCALIZED TURBULENCE. TONIGHT
ANTICIPATE WIDESPREAD REDEVELOPMENT OF LOW CLOUDS IN THE IFR TO MVFR
RANGE...ALTHOUGH TRUE FOG WILL BE QUITE LIMITED. /BB/
PREV DISCUSSION
/ISSUED 420 AM CDT SAT MAY 18 2013/
SHORT TERM...TODAY THROUGH SUNDAY NIGHT...ASIDE FROM THE EARLY
MORNING/ONGOING CONVECTION...THE SHORT TERM PORTION OF THE FORECAST
WILL BE QUIET AND BEST CHARACTERIZED AS EARLY SUMMER LIKE THANKS TO
THE WARM/HUMID CONDITIONS THAT ARE EXPECTED.
EARLY THIS MORNING WE HAVE LINGERING CONVECTION (SOME HAVE BEEN
STRONG TO SVR) ACROSS THE NE/GOLDEN TRIANGLE REGION OF THE CWA. THIS
ACTIVITY HAS BEEN FOCUSING ON AN OLD BOUNDARY FROM FRIDAY MORNINGS
ACTIVITY AND THEN INVIGORATED BY SOLID MOISTURE ADV ATOP THE
BOUNDARY AND SOME ASSISTED LIFT FROM A S/WV MOVING THROUGH N MS.
THIS ACTIVITY WILL LINGER A BIT THIS MORNING BUT ONLY EXPECT IT TO
LAST THROUGH 6-8 AM AND BE FOCUSED ACROSS THE FAR NE CWA.
FOR THE REST OF THE CWA AND EVEN OUR FAR NE AFTER THIS MORNING
ACTIVITY EXITS...LOOK FOR PRECIP FREE CONDITIONS AS ATMOSPHERIC
CAPPING BUILDS OVER THE AREA. IN TANDEM WITH THIS...DRY ADV WILL
OVERTAKE THE AREA IN THE LOW LEVELS AND KEEP ANY PRECIP AT BAY. I
WILL ONLY MENTION POPS/WX THIS MORNING TO ACCOUNT FOR THE EARLY AM
ACTIVITY THEN KEEP THE GRIDS WX FREE FOR THE AFTERNOON.
DESPITE THE DRY AIR ADV JUST OFF THE SFC AND IN THE CAPPING
LAYER...BOUNDARY LAYER MOISTURE WILL REMAIN HIGH WITH DEWPTS
CONTINUING TO RUN IN THE UPPER 60S TO AROUND 70 DEGREES. THIS WILL
KEEP THAT HUMID FEELING IN THE AIR. THE CAPPING LAYER WILL ALSO
SERVE TO SUPPORT LOW STRATUS IN THE MORNING...BUT GIVE WAY TO FEW OR
NO CLOUDS DURING THE DAY. THIS WILL HELP WITH STRONG SFC HEATING
BOTH TODAY AND SUNDAY (ESP SUNDAY).
LONG TERM...MONDAY THROUGH SATURDAY...MEDIUM RANGE MODELS ARE IN
FAIR AGREEMENT AT THE START OF THE LONG TERM WITH A CLOSED LOW OVER
THE NORTHERN PLAINS AND A POTENT SHORTWAVE DROPPING OVER THE FOUR
CORNERS REGION. THESE FEATURES WILL SUPPORT A COLD FRONT THAT WILL
DROP INTO OUR CWA WEDNESDAY AND GIVE US OUR NEXT BEST CHANCE FOR
RAIN. AHEAD OF THIS SYSTEM...SHORTWAVE RIDGING ALOFT AND A SURFACE
RIDGE OVER THE GULF COAST WILL BE DOMINANT MONDAY OVER OUR CWA.
MODEL SOUNDINGS INDICATE SOME EARLY MORNING STRATUS AND A DECENT
CAP. THE CAP MAY HOLD BUT THE STRATUS SHOULD BURN OFF RAPIDLY AND A
WARM AND HUMID DAY IS EXPECTED. WARMER THAN NORMAL AFTERNOON HIGHS
IN THE UPPER 80S AT MOST SITES WILL COMBINE WITH UPPER 60 DEGREE DEW
POINTS. BY TUESDAY PWS IN THE WEST ARE EXPECTED TO EXCEED AN INCH
AND A HALF WITH A WEAKER CAP IN PLACE. DAYTIME HEATING SHOULD LEAD
TO SCATTERED MAINLY AFTERNOON AND EVENING CONVECTION. THERMODYNAMIC
PARAMETERS INDICATE POTENTIAL FOR A FEW STRONG STORMS OVER THE DELTA
REGION. THE GFS AND ECMWF AGREE THAT THE COLD FRONT WILL MOVE INTO
OUR WESTERN ZONES WEDNESDAY AND THAT THE CLOSED LOW WILL OPEN UP
INTO A WEAKENING TROUGH AS IT MOVES ACROSS OUR REGION BUT THEY
DIFFER SIGNIFICANTLY ON TIMING AND PROGRESSION OF THE COLD FRONT.
THE GFS BRINGS THE COLD FRONT THROUGH OUR CWA BY THURSDAY MORNING
WHILE THE ECMWF STALLS THE FRONT AND DISSIPATES IT BY THURSDAY
MORNING. EITHER WAY STRONG TO SEVERE STORMS LOOK POSSIBLE OVER THE
WESTERN PORTIONS OF THE AREA AGAIN WEDNESDAY. HAVE LEANED TOWARD
THE GFS THIS FCST AND WL RESULT IN COOLER AND DRIER WEATHER FOR
THURSDAY AND FRIDAY. BOTH GFS AND ECMWF SHOW A SECOND CLOSED LOW
DEVELOPING OVER THE OHIO VALLEY FRIDAY RESULTING IN AN OMEGA BLOCK
WITH THE RIDGE OVER THE CENTRAL CONUS GOING INTO NEXT WEEKEND. THIS
WOULD RESULT IN CONTINUED NORTHWEST FLOW ALOFT OVER OUR REGION AND
COOLER THAN NORMAL TEMPERATURES INTO NEXT WEEKEND. /22/
AVIATION
MAIN ISSUE THIS MORNING WILL BE MVFR CEILINGS WITH A FEW
SITES SEEING A PERIOD OF IFR CEILINGS. THESE CEILINGS ARE NOT
EXPECTED TO LINGER TOO LONG AND IMPROVE TO VFR BETWEEN 15-17Z. VFR
CONDITIONS WILL LINGER FOR THE MAJORITY OF THE DAY.
HOWEVER...ANOTHER ROUND OF STRATUS IS EXPECTED TONIGHT. LOOK FOR IFR
CEILINGS TO AGAIN BE POSSIBLE AND LIKELY BEGIN AFTER 07-09Z. /CME/
PRELIMINARY POINT TEMPS/POPS
JACKSON 89 68 88 70 / 0 2 0 0
MERIDIAN 87 68 87 67 / 16 14 0 0
VICKSBURG 88 69 88 69 / 0 2 0 0
HATTIESBURG 89 69 87 69 / 8 6 0 0
NATCHEZ 87 69 87 70 / 0 2 0 0
GREENVILLE 87 70 89 70 / 1 2 0 0
GREENWOOD 87 68 89 70 / 9 6 0 0
JAN WATCHES/WARNINGS/ADVISORIES
MS...NONE.
LA...NONE.
AR...NONE.
DC/BB/22/CME
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