Area Forecast Discussion
Issued by NWS Jackson, MS

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FXUS64 KJAN 270311 AAA
AFDJAN

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE JACKSON MS
911 PM CST FRI DEC 26 2014

.UPDATE...
THE PRECIP HAS PRETTY MUCH CEASED IN OUR AREA FOR NOW. MOISTURE WILL
CONTINUE TO BUILD INTO THE AREA OVERNIGHT THOUGH AND ISENTROPIC
ASCENT WILL INCREASE. LOOKING AT SOME OF THE HI-RES MODELS...THE ARW
AND HRRR SPECIFICALLY...A LULL IS INDICATED IN THE HOURS BETWEEN 00Z
AND 09Z. THIS SEEMS TO BE THE PRESENT CASE SO THEREFORE IT HAS BEEN
REFLECTED IN OUR POPS GRIDS. PRECIP WILL GRADUALLY BUILD BACK INTO
OUR AREA FROM THE SOUTHWEST BEFORE 12Z. THE HOURLY TEMPS AND DEWPOINTS
WERE ADJUSTED FOR THIS UPDATE. OTHERWISE...THE GOING FORECAST SEEMS
TO BE PRETTY GOOD. /10/

&&

.AVIATION...
INTERMITTENT LIGHT RAIN WL CONT TO SPREAD ACROSS THE AREA FROM THE
SW AND BRING BRIEF VSBY RESTRICTIONS BUT VFR CONDITIONS WL PREVAIL AT
MOST TAF SITES THROUGH 12Z SAT. THE EXCEPTION WL BE GLH WHERE IFR
CIGS ARE EXPECTED BEFORE 12Z SAT. CIGS WL LOWER TO IFR CONDS ALONG
WITH REDUCED VSBYS SAT MORNING AS WIDESPREAD RAIN DEVELOPS OVER THE
AREA. ISOLD TSTMS WL BE PSBL LATE SAT AFTN SE. IFR/LIFR CONDS WL
PREVAIL SATURDAY NIGHT THROUGH SUNDAY MORNING. /22/

&&

.PREV DISCUSSION... /ISSUED 413 PM CST FRI DEC 26 2014/

SHORT TERM...

..FRIDAY NIGHT THROUGH MONDAY MORNING...

RAINFALL IS SLOWLY INCREASING THIS AFTERNOON AND WILL CONTINUE
THROUGH THE AFTERNOON AND ESPECIALLY INTO TONIGHT. CLOUDS WILL
CONTINUE TO INCREASE FROM THE W AS ISENTROPIC LIFT/MOISTURE
TRANSPORT SLOWLY INCREASES FROM THE W/SW. CLOUDS WILL FILL IN
TONIGHT ACROSS THE AREA...KEEPING LOWS IN THE MID 50S IN THE W TO
WHILE SLOWER MOVEMENT INTO THE E LOWS WILL DROP INTO THE UPPER 40S.

AS THE SFC COLD FRONT SLOWLY PROGRESSES SE THROUGH THE CENTRAL PLAINS
AND 80-100KT+ H3 JET/UPPER DIFFLUENCE AID IN INCREASING LIFT...EXPECT
INCREASING MOISTURE TRANSPORT BEGINNING TONIGHT IN OUR THE REGION.
EURO/GFS ARE IN GOOD AGREEMENT THAT ANOMALOUS PW`S...SOME 2-3
STANDARD DEVIATIONS ABOVE NORMAL AND THE 99TH PERCENTILE....WILL
BEGIN TO MOVE INTO THE REGION BEGINNING LATE TONIGHT. THE LONGWAVE
TROUGH OVER THE ROCKIES/NRN PLAINS WILL ONLY SLOWLY MOVE E DUE TO THE
BLOCKING OF THE 590+DM H5 RIDGE OVER SW ATLANTIC. THIS SETUP WILL PUT
THE REGION IN A FAVORABLE SYNOPTIC PATTERN FOR HEAVY RAIN AND SOME
LOCALIZED FLASH FLOODING ...BETWEEN DEEP LONGWAVE TROUGH/SW FLOW
ALOFT/STRONG SE UPPER RIDGE. AS THE SFC LOW PRESSURE SLOWLY DEVELOPS
ALONG THE GULF COAST...MOVES TO THE NE AND THE COLD FRONT SLOWLY
MOVES INTO THE AREA LATE THIS WEEKEND...HEAVY RAIN WILL CONTINUE
SATURDAY AND INTO SUNDAY NIGHT. MODELS CONTINUE TO INDICATE THAT
THERE COULD BE SOME RAINFALL TOTALS BETWEEN 2-4 INCHES. 18Z NAM/HI-
RES ARW/NMM ARE INDICATING EVEN HIGHER AMOUNTS WITH SOME IN EXCESS OF
4-5 INCHES AND SHIFTED SLIGHTLY N TOWARDS THE JACKSON METRO AREA. IN
AREAS WHERE CONVECTIVE DEVELOPMENT CAN OCCUR...WHICH IS POSSIBLE DUE
TO ELEVATED INSTABILITY/MAUL ENVIRONMENTS...THIS IS NOT OUT OF
QUESTION. MAIN AREA OF CONCERN LOOKS TO REMAIN ALONG/SE OF THE
NATCHEZ TRACE CORRIDOR WHERE THE BEST MOISTURE TRANSPORT/ISENTROPIC
LIFT WILL RESIDE. RAIN WILL CONTINUE THROUGH THE WEEKEND WHILE THE
HEAVIEST LOOKS TO MOVE INTO OUR AREA BETWEEN 18-00Z SUNDAY. EXPECT
RAINFALL TO MOVE OUT OF THE AREA EARLY MONDAY MORNING AS THE COLD
FRONT MOVES THROUGH. LATER SHIFTS WILL MONITOR THE POTENTIAL FOR
FLASH FLOOD WATCH IF GLOBAL/HI-RES GUIDANCE CONTINUE TO INDICATE
POTENTIAL FOR EVEN HIGHER AMOUNTS. HWO/GRAPHICS ARE OUT HIGHLIGHTING
THE LIMITED HEAVY RAIN POTENTIAL.

ALSO OF RELEVANCE IS THE LIMITED POTENTIAL FOR SOME SEVERE WEATHER
IN THE HWY 84 CORRIDOR BOTH SATURDAY AND SUNDAY. MAIN AREA FOR
SATURDAY WILL BE IN NE LA/SW MS WHILE SHIFTING INTO THE SE PORTIONS
OF THE AREA SUNDAY. DEWPOINTS IN THE LOWER 60S AND BETTER LAPSE
RATES/SOME POTENTIAL SFC INSTABILITY WILL RESIDE WITH EFFICIENT
0-1KM AND 0-3KM BULK SHEAR APPROACHING 25-35KTS OR SLIGHTLY HIGHER.
THIS WILL DEPEND ON THE EVENTUAL TRACK OF THE LOW ON WHERE THE MOST
EFFICIENT WIND PROFILES WILL RESIDE BUT THIS AREA IN NE LA/SRN MS
CONTINUES TO REMAIN FAVORABLE. INSTABILITY WILL BE LOWER THAN
EARLIER THIS WEEK AND THUS ONLY A LIMITED CHANCE EXISTS FOR SEVERE
WEATHER THIS WEEKEND. HWO/GRAPHICS ARE OUT HIGHLIGHTING THE SEVERE
POTENTIAL.

AS THE UPPER RIDGE WEAKENS...THE LOW PRESSURE WILL MOVE TO THE NE
LATE SUNDAY NIGHT AND INTO MONDAY AND THE UPPER TROUGH WILL
GRADUALLY SWING THROUGH...BRINGING THE COLD FRONT THROUGH THE
REGION. TEMPERATURES WILL FALL INTO THE UPPER 30S IN THE NW DELTA
WHILE ONLY IN THE 50S IN THE SE. FOR FORECAST ELEMENTS...WENT WARMER
TONIGHT IN W/SW DUE TO CLOUDS/PRECIP MOVING IN. WENT SLIGHTLY COOLER
SATURDAY NEAR EURO DUE TO RAIN/OVERCAST CONDITIONS. WENT CLOSER TO
RAW GUIDANCE SATURDAY AND INTO MONDAY AS GUIDANCE WILL HANDLE THE
TEMPS WITH THE FRONTAL PASSAGE BETTER THAN MOS. RELEVANT PORTION OF
THE PREVIOUS LONG TERM DISCUSSION IS ATTACHED. /DC/

LONG TERM...

..MONDAY INTO LATE NEXT WEEK...

EXPECT COOLER AND DRIER WEATHER BEHIND THE FRONT FOR THE MON NIGHT
THROUGH TUES NIGHT PERIOD WITH TEMPERATURES GENERALLY NEAR SEASONAL
AVERAGES. AS WE GO INTO MID WEEK...MODELS ARE IN GENERAL AGREEMENT
THAT A MASSIVE ARCTIC AIRMASS WILL SURGE SOUTHWARD THROUGH THE
PLAINS AND EXPAND INTO THE LOWER MS VALLEY REGION NEW YEAR`S EVE.
THE LARGEST TEMPERATURE ANOMALIES ARE EXPECTED TO STAY WEST OF THE
ARKLAMISS BASED ON THE PRESSURE PATTERN...BUT IT WILL BE SUCH A
STRONG HIGH PRESSURE CENTER THAT SUFFICIENTLY COLD AIR FOR WINTER
WEATHER POTENTIAL MAY EXIST INTO NORTHERN PORTIONS OF THE AREA AS
SOUTHWEST FLOW JUXTAPOSES THE SHALLOW MODIFYING ARCTIC AIR.

ALTHOUGH GFS/ECMWF ARE BEARISH WITH QPF FOR MID/LATE WEEK...THE
AIRMASS OVER THE GULF WILL CONTINUE TO BE UNSEASONABLY MOIST AND
PRIME FOR QUICK NORTHWARD TRANSPORT WITH THE SLIGHTEST DISTURBANCE
AND BACKING OF LOW LEVEL FLOW GIVEN THE STRONG GULF COAST BAROCLINIC
ZONE. GUIDANCE IS SLIGHTLY SLOWER ON MOISTURE RETURN ON NEW YEARS EVE
AND ONLY INCLUDED MENTION OF RAIN FOR NOW. HOWEVER...THERE EXISTS A
POSSIBILITY SOME OF THAT MOISTURE COULD MOVE FURTHER N OVER TOP THE
SHALLOW ARCTIC AIRMASS...WHICH COULD BRING THE CHANCE FOR WINTRY
PRECIP. WE WILL CLOSELY MONITOR THAT POSSIBILITY. IT DOES NOT APPEAR
THE ARKLAMISS WILL EXPERIENCE OVERLY COLD TEMPERATURES GIVEN THE
TREND FOR INCREASING SOUTHERN STREAM SEPARATION/DOMINANCE AND NRN
STREAM RETREAT. /EC/DC/

&&

HYDROLOGY...WILL CONTINUE MENTION OF 2-4 INCHES OF RAIN ACROSS THE
SOUTHEASTERN PORTION OF OUR FORECAST AREA IN OUR GRAPHICS AND THE
HAZARDOUS WEATHER OUTLOOK. THIS RAIN MAY HAVE SOME IMPACT SINCE IT
FOLLOWS SO CLOSELY BEHIND THE HEAVY RAIN THAT FELL IN THAT REGION ON
TUESDAY. RAINFALL RATES WILL BE CRITICAL AS TO WHETHER THIS BECOMES
A FLASH FLOODING EVENT OR JUST A SOAKING RAIN.

CONTINGENCY FORECASTS COMPLETED BY THE LOWER MISSISSIPPI RIVER
FORECAST CENTER FOR AREA RIVERS INDICATE THAT EVEN WITH THIS HEAVY
RAINFALL...RIVERS SHOULD REMAIN MOSTLY BELOW FLOOD STAGE. IF THE
RAIN IS A BIT HEAVIER THAN EXPECTED...A FEW RIVER POINTS MAY REACH
INTO THE MINOR FLOOD CATEGORY. OVERALL RIVER IMPACT IS EXPECTED TO
BE LOW.

HAVE ISSUED A HYDROLOGIC OUTLOOK AS A PREVIEW FOR A POTENTIAL FLOOD
WATCH. /SW/

&&

.PRELIMINARY POINT TEMPS/POPS...
JACKSON       53  63  59  60 /  55 100  94  89
MERIDIAN      48  59  56  65 /  32 100  95  81
VICKSBURG     55  66  53  54 /  65 100  92  85
HATTIESBURG   53  63  63  70 /  45 100  95  70
NATCHEZ       57  67  56  57 /  65 100  94  83
GREENVILLE    53  63  46  50 /  61 100  89  61
GREENWOOD     53  61  50  52 /  42 100  92  73

&&

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

$$





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