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Area Forecast Discussion

567
FXUS64 KHUN 042057
AFDHUN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HUNTSVILLE AL
257 PM CST WED MAR 4 2015

.DISCUSSION...
THE 21Z SURFACE ANALYSIS INDICATED THAT THE COLD FRONT WAS EXTENDING
NORTHEAST FROM NEAR CORINTH MISSISSIPPI AND BARELY INTO THE FORECAST
AREA IN NORTHWEST ALABAMA NEAR FLORENCE...TO NEAR FAYETTEVILLE
TENNESSEE. A LARGE AREA OF MAINLY LIGHT TO MODERATE RAIN WAS MAINLY
ALONG AND BEHIND THE COLD FRONT ACROSS MUCH OF NORTHERN MISSISSIPPI
AND THROUGHOUT WEST AND MIDDLE TENNESSEE.

EXPECT SHOWERS/EMBEDDED STORMS TO CONTINUE TO INCREASE IN COVERAGE
ACROSS THE FORECAST AREA INTO THE EARLY-MID EVENING AS THE COLD FRONT
MOVES THROUGH THE FORECAST AREA. THE SHORT TERM MODELS ARE FAIRLY
SIMILAR INVOLVING HAVING THE COLD FRONT MOVE THROUGH THE AREA BY
AROUND 03Z TONIGHT. A WINTER STORM WARNING REMAINS IN EFFECT FOR THE
FORECAST AREA FROM 09Z-21Z ON THURSDAY. STRONG COLD ADVECTION WILL
IMMEDIATELY FILTER SOUTHEAST INTO THE FORECAST AREA BEHIND THE COLD
FRONT THROUGH THE OVERNIGHT HOURS. HAVE SLIGHTLY ADJUSTED THE TIMING
FORWARD OF THE EXPECTED TRANSITION FROM RAIN TO FREEZING RAIN BASED
UPON THE LOW LEVEL DEPTH OF THE COLD ADVECTION AS PER NAM/GFS BUFR
SOUNDINGS. TIMING OF THE FREEZING RAIN ONSET WOULD BE FROM AROUND
08Z-09Z IN NORTHWEST ALABAMA...TO AROUND 10Z FROM CULLMAN COUNTY
EXTENDING NORTHEAST THROUGH MARSHALL TO JACKSON COUNTIES AND AROUND
11Z IN DEKALB COUNTY IN NORTHEAST ALABAMA.

FORECAST SOUNDINGS INDICATE THAT FREEZING RAIN SHOULD COMBINE WITH
AND CHANGE OVER TO ALL SLEET BY BETWEEN THE 14Z-16Z TIME FRAME IN
THE MORNING. BY THIS TIME PERIOD...THE LOWER LAYER AT OR BELOW 900
MILLIBARS COOLS BELOW FREEZING SUFFICIENTLY ENOUGH FOR CONDITIONS TO
BE MORE CONDUCIVE FOR SLEET ACROSS THE FORECAST AREA. SOME OF THE
AREA WILL SEE SLEET AMOUNTS UP TO A HALF OF AN INCH...WITH GENERALLY
LIGHT SNOW AMOUNTS EXPECTED BETWEEN LATE MORNING AND INTO THE
AFTERNOON HOURS. THE MODELS ARE AGAIN TODAY SLIGHTLY SLOWER INVOLVING
THE PRECIP EXITING THE REGION BY AFTERNOON. WILL KEEP TEMPS NEARLY
STEADY DURING THE DAY CLOSE TO MODEL GUIDANCE NUMBERS.

COLD HIGH PRESSURE WILL PROGRESSIVELY SHIFT SOUTHEAST ACROSS THE
REGION ON FRIDAY...WITH VERY COLD MORNING TEMPS AT AROUND 25 DEGREES
BELOW NORMAL EXPECTED. THE GFS AND ECMWF MODELS SHIFT THE HIGH
PRESSURE RIDGE AXIS SLIGHTLY EAST OF THE FORECAST AREA BY SATURDAY
AFTERNOON...WITH A LOW LEVEL SOUTHERLY FLOW EXPECTED.

TEMPS WILL FINALLY GET CLOSE TO NORMAL BY SUNDAY AND MONDAY...WITH A
MID TO UPPER LEVEL SOUTHWEST FLOW CONTINUING INTO THE EARLY PART OF
NEXT WEEK. THE GFS AND ECMWF MODELS DIFFER INVOLVING THE NORTHWARD
MOVEMENT OF LOW LEVEL MOISTURE OUT OF THE GULF OF MEXICO ALONG AND
AHEAD OF AN AREA OF LOW PRESSURE IN THE NORTHERN GULF OF MEXICO. THE
ECMWF MODEL KEEPS THE FORECAST AREA NORTH OF A WEAK AREA OF LOW
PRESSURE IN THE GULF OF MEXICO BETWEEN MONDAY THROUGH WEDNESDAY. THE
GFS MODEL INDICATES A MORE NORTHWARD MOVEMENT OF LOW LEVEL
MOISTURE/PRECIP INTO THE FORECAST AREA DURING THIS TIME FRAME. HAVE
GONE WITH A COMPROMISE BETWEEN THE MODELS AND HAVE KEPT IN LOW
CHANCES FOR THE FORECAST AREA THROUGH THE LATTER PART OF THE EXTENDED
FORECAST PERIODS. WILL STAY CLOSER TO THE ECMWF MODEL TEMP GUIDANCE
THROUGH THE EXTENDED FORECAST TIME FRAME.

TT

&&

.AVIATION...
/ISSUED 1144 AM CST WED MAR 4 2015/
FOR 18Z TAFS...STILL EXPECTING VCSH FOR THE NEXT FEW HOURS WITH -RA
MOVING INTO KMSL BY 19Z AND KHSV BY 22Z DUE TO A SLOW MOVING FRONT
THAT IS SINKING SOUTHEAST. AN ISOLATED THUNDERSTORM IS POSSIBLE BUT
CONFIDENCE IS TOO LOW ON LOCATION TO INCLUDE IN TAFS. RAIN COULD BE
MODERATE TO HEAVY AT TIMES AFTER 23/00Z AND WILL TRANSITION TO
FREEZING RAIN AROUND 9-11Z. AS WITH MOST WINTER EVENTS...THIS TIMING
COULD EASILY SHIFT IN EITHER DIRECTION BASED ON HOW THE TEMPERATURES
TREND. FZRA SHOULD THEN TRANSITION TO -IP/SN BY MORNING WITH POSSIBLY
A HALF AN INCH OF SLEET ACCUMULATION AFTER 14/16Z BEFORE IT ENDS.
WINDS WILL BE GUSTY THROUGH THE PERIOD WITH A FEW BRIEF LULLS
POSSIBLE.

LN

&&

.PRELIMINARY POINT TEMPS/POPS...
HUNTSVILLE    27  30  21  40 / 100  80  10   0
SHOALS        25  29  18  39 / 100  70  10   0
VINEMONT      28  31  21  38 / 100  80  10   0
FAYETTEVILLE  25  28  17  37 / 100  70  10   0
ALBERTVILLE   32  33  22  42 / 100  80  10   0
FORT PAYNE    34  35  22  42 / 100  80  10   0

&&

.HUN WATCHES/WARNINGS/ADVISORIES...
AL...WINTER STORM WARNING FROM 3 AM TO 3 PM CST THURSDAY FOR ALZ001>010-
     016.

TN...WINTER STORM WARNING FROM 3 AM TO 3 PM CST THURSDAY FOR TNZ076-096-
     097.

&&

$$

FOR MORE INFORMATION PLEASE VISIT OUR WEBSITE
AT WEATHER.GOV/HUNTSVILLE.



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