Area Forecast Discussion
Issued by NWS Jackson, MS

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FXUS64 KJAN 180224 AAA
AFDJAN

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE JACKSON MS
924 PM CDT FRI APR 17 2015

.UPDATE...EXPECTING ONLY SLIGHT CHANCES FOR SHOWERS/STORMS OVERNIGHT
BEFORE BETTER CHANCES ARRIVE TOMORROW. LOW TEMPERATURES TONIGHT WILL
BE IN THE 60S. AS FOR THE CURRENT FORECAST...ADDED PATCHY FOG TO THE
CWA FOR LATER TONIGHT INTO EARLY TOMORROW MORNING...AND MADE MINOR
CHANGES TO THE HOURLY TEMPS FOR THIS EVENING. /27/

&&

.AVIATION...EXPECT A REPEAT OF IFR CATEGORY STRATUS AND PERHAPS SOME
FOG LATER TONIGHT PERSISTING THROUGH EARLY MORNING BEFORE MIXING UP
TO MVFR AND EVENTUALLY VFR CATEGORY BY EARLY AFTERNOON. SHRA/TSRA
COULD BECOME WIDESPREAD BY AFTERNOON LASTING INTO THE EVENING WITH
APPROACHING SHORTWAVE TROUGH...SO EXPECT A POOR DAY FOR FLYING
OVERALL. /EC/


&&

.PREV DISCUSSION... /ISSUED 500 PM CDT FRI APR 17 2015/

DISCUSSION...SUBSIDENCE IN THE WAKE OF OVERNIGHT MCV HAS KEPT
CONVECTION AT BAY FOR THE MAJORITY OF THE AFTERNOON AND SCOURED OUT
THE HIGHER DEWPOINTS WE HAVE HAD THE LAST FEW DAYS. THE EXCEPTION
HAS BEEN A FEW STORMS IN E MS ALONG A LEFT OVER CONVERGENT BOUNDARY
IN CLOSE PROXIMITY TO NOSE OF 300 MB 75 KNOT JET STREAK. WHILE LAPSE
RATES ARE NOT THAT IMPRESSIVE AT THE MOMENT...CAPES AROUND 2000 J/KG
AND 25-30 KNOTS OF DEEP LAYER SHEAR COULD ALLOW FOR A FEW STORMS TO
BECOME STRONG.

SHORTWAVE RIDGING WILL ALLOW FOR A QUIET OVERNIGHT ONCE THE EVENING
CONVECTION SUBSIDES. MID/UPPER LEVEL SW FLOW WILL CRANK BACK UP EARLY
SATURDAY MORNING IN ADVANCE OF STRONG SYSTEM MOVING OUT OF THE
ROCKIES. MODEL DATA SHOWING OVERNIGHT CONVECTIVE AREA OVER THE UPPER
TX/LA COAST ALONG MARINE LAYER BOUNDARY WITH STRATIFORM PRECIP
BEGINNING TO ENTER THE SW AT DAWN.

QUESTION MARKS EXIST AT PRESENT FOR SEVERE POTENTIAL SATURDAY.
PRESENTLY...CONVECTIVE BLOB EXPECTED TO DEVELOP AND MOVE EAST ALONG
THE NORTHERN GULF COAST OVERNIGHT. IF THIS SLOWS DOWN AND STAGNATES
ALONG THE MS/LA COAST...BACKING OF LOW LEVEL WIND FIELD AND ADVANCE
OF MARINE LAYER NORTHWARD MAY NOT OCCUR. PRESENTLY EXPECTING THE
CONVECTION TO CONTINUE RACING EASING EAST ALONG ITS DIFFERENTIAL
DIVERGENCE BULLSEYE. THIS WILL ALLOW THE ATMOSPHERE TO RESET QUICKER
WITH BACKING LOW LEVEL WINDS AND THE MARINE LAYER BOUNDARY ADVANCING
NORTHWARD DURING THE AFTERNOON. MLCAPES FROM 1500-2000 J/KG WILL
POOL ALONG THE BOUNDARY AS IT PUSHES NORTH FROM S LA/S MS...BUT LAPSE
RATES ARE NEARLY MOIST ADIABATIC IN THE DEEP TROPICAL AIRMASS (PW
VALUES NEAR 2 IN). NEVERTHELESS...0-1 KM SRH VALUES ARE RANGING FROM
250-300 M2/S2 IN CLOSE PROXIMITY TO THE BOUNDARY WITH LOW LCLS WHICH
SHOULD ALLOW FOR THE DEVELOPMENT OF A FEW TORNADOES. SOME THREAT OF
WIND AS WELL FROM PRECIP LOADING...BUT TORNADOES AND HEAVY RAINFALL
ARE PRIMARILY EXPECTED.

WHILE THE HEAVY RAINFALL RISK WILL CONTINUE INTO THE EVENING AS THE
CONVECTIVE AREA MOVES NE...TORNADO RISK WILL BE DIMINISHING WITH THE
LOSS OF ANY REMAINING INSTABILITY. /26/

MODELS FOR SUNDAY CONTINUE TO SUPPORT THE RISK FOR SEVERE STORMS
ALONG WITH SOME POTENTIAL FOR A HIGHER END EVENT. WHAT IS STARTING TO
BECOME MORE CLEAR IS MUCH OF THE DAY LOOKS TO BE IN A LULL FROM
CONVECTION AFTER MORNING ACTIVITY DEPARTS TO THE EAST AND THE ROUND
OF STORMS WILL BE MORE FOCUSED LATER BETWEEN A 5PM TO 3AM WINDOW. IN
THE WAKE OF THE SAT SYSTEM...MUCH STEEPER LAPSE RATES WILL SPREAD
OVER THE AREA (7.0 TO 7.5 C/KM)(29-31C VERTICAL TOTALS). ALOFT MUCH
COLDER TEMPS WILL MOVE IN WITH H5 READINGS OF -15 TO - 16C. THIS WILL
ALL SUPPORT SBCAPE OF 2000-3000 J/KG AS SFC HEATING REACHES AROUND 80
DEGREES. THIS WILL ALL SUPPORT VIGOROUS STORMS WITH ROBUST UPDRAFTS.
CONCURRENT WITH THIS WILL BE AN OVERALL DRIER ATMOSPHERE COLUMN AS
WELL WITH PWS AROUND 1.2 INCHES. THIS WILL LEND TO KEEPING STORMS
MORE DISCRETE ALONG WITH AN EASTWARD DEEP LAYER (0-6KM) SHEAR VECTOR
OF 40-50KTS. EXPECTATIONS ARE FOR NOT MANY (ISO/SCT) SUPERCELLS THAT
WILL PACK QUITE THE PUNCH. LARGE HAIL > GOLF BALL SIZE APPEARS VERY
POSSIBLE ALONG WITH DAMAGING WINDS WHICH ALSO COULD BE HIGHER END.
DUE TO THIS POSSIBILITY OF SEEING SIGNIFICANT TYPE WEATHER (>2 IN
HAIL)...WILL UP OUR OUTLOOK TO SIG OVER A DECENT PORTION OF THE NW.
ELSEWHERE THE OUTLOOK WILL REMAIN SIMILAR AS STORMS MAY LOSE SOME
POTENCY AS THEY PUSH FURTHER EAST AND GET LATER INTO THE OVERNIGHT.
/CME/


&&

.PRELIMINARY POINT TEMPS/POPS...
JACKSON       63  73  63  80 /  18  86  69  40
MERIDIAN      61  75  66  80 /  17  86  77  47
VICKSBURG     63  74  61  81 /  24  86  72  40
HATTIESBURG   64  74  68  83 /  24  86  65  49
NATCHEZ       65  74  62  81 /  36  86  54  40
GREENVILLE    62  75  61  78 /  17  72  79  39
GREENWOOD     61  75  63  79 /  18  68  83  38

&&

.JAN WATCHES/WARNINGS/ADVISORIES...
MS...NONE.
LA...NONE.
AR...NONE.
&&

$$



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