Area Forecast Discussion
Issued by NWS Huntsville, AL

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FXUS64 KHUN 031214
AFDHUN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HUNTSVILLE AL
614 AM CST TUE MAR 3 2015

.UPDATE...
FOR 12Z TAFS

&&

.DISCUSSION...
/ISSUED 414 AM CST TUE MAR 3 2015/

ZONAL FLOW PERSISTS IN THE LOW TO MID LEVELS ACROSS THE
SOUTHEAST...WHILE A DEEP UPPER LEVEL CLOSED LOW SITS OVER CANADA AND
A SECOND LOW SITS OFF THE COAST OF CALIFORNIA. AT THE SURFACE...THE
COLD FRONT THAT MOVED THROUGH YESTERDAY MORNING IS CURRENTLY STALLED
ACROSS SOUTHERN GEORGIA AND SOUTHERN ALABAMA...WHILE THE SURFACE
HIGH HAS MOVED NORTHEAST..WITH THE CENTER OVER PENNSYLVANIA. AS THIS
HIGH CONTINUES TO PUSH EAST...WINDS WILL BEGIN TO SHIFT MORE
SOUTHERLY...WITH THE STALLED FRONT EXPECTED TO LIFT NORTHWARD
THROUGH THE DAY. THE UPPER TROUGH WILL BEGIN TO MOVE ASHORE LATER
THIS MORNING...WITH WEAK UPPER LEVEL RIDGING EXPECTED TO BUILD OVER
THE SOUTHEAST. THIS WILL SET THE AREA UP FOR A PERIOD OF VERY STRONG
DEEP LAYER WAA OVER THE NEXT 24 HOURS. TEMPERATURES CURRENTLY IN THE
MID TO UPPER 40S WILL RISE AT LEAST 15 DEGREES BY THE
AFTERNOON...AND HIGHS IN THE UPPER 60S ARE LIKELY. SHOWERS WILL BE
POSSIBLE DURING THE DAY...AS THE WARM FRONT LIFTS
NORTHWARD...HOWEVER THUNDERSTORMS LOOK TO BE MINIMAL GIVEN THE LACK
OF INSTABILITY...DUE TO THE VERY POOR LAPSE RATES IN THE LOW TO MID
LEVELS.

THE PRIMARY FOCUS CONTINUES TO BE ON THE STRONG COLD FRONT THAT WILL
BE MOVING THROUGH THE AREA ON WEDNESDAY. THE CLOSED LOW OVER CANADA
WILL MOVE SOUTHEAST...WHILE THE CLOSED LOW OFF THE CALIFORNIA COAST
CONTINUES TO MOVE EAST THROUGH THE DESERT SOUTHWEST. A STRONG COLD
FRONT DEVELOPS SOUTH OF THE PARENT SURFACE LOW THAT WILL PUSH EAST
OVER THE GREAT LAKES LATER THIS EVENING. AS THE COLD FRONT INCHES
CLOSER TO THE AREA...SHOWERS AND ISOLATED THUNDERSTORMS WILL DEVELOP
WEDNESDAY MORNING AHEAD OF THE COLD FRONT. TEMPERATURES WILL REMAIN
IN THE UPPER 50S TO LOWER 60S...SO AN ISOLATED STRONG STORM IS
POSSIBLE...HOWEVER THE THREAT FOR ANY WIDESPREAD STRONG TO SEVERE
STORMS IS VERY LIMITED. MODEL CONSENSUS IS COMING MORE IN LINE WITH
THE TIMING OF THE COLD FRONT...HOWEVER THERE ARE STILL SOME
DISCREPANCIES...WHICH MAKES FOR A VERY DIFFICULT AND UNCERTAIN
FORECAST.

STRONG SOUTHERLY FLOW WILL CONTINUE AHEAD OF THE COLD FRONT...AND
THE FRONT MAY HAVE A DIFFICULT TIME OVERCOMING THE WARM AIRMASS IN
PLACE. WITH THAT SAID...HAVE DECIDED TO CONTINUE WITH A BLEND OF THE
GFS AND THE ECMWF...WITH FRONTAL PASSAGE OCCURRING DURING THE
AFTERNOON ACROSS THE NORTHWEST...AND CLEARING THE AREA JUST BEFORE
MIDNIGHT. AS STATED ABOVE..MODELS ARE INDICATING THAT THE COLD ARCTIC
AIR MAY HAVE A HARD TIME FILTERING INTO THE FORECAST AREA...EVEN
AFTER FRONTAL PASSAGE. AN ABUNDANCE OF MOISTURE WILL BE LOCATED JUST
AHEAD AND BEHIND THE FRONT...WITH A VERY STRONG UPPER LEVEL JET
PROVIDING CONTINUED LIFT ACROSS THE AREA. THEREFORE WIDESPREAD
SHOWERS WILL BE ONGOING THROUGH MUCH OF THE DAY AND OVERNIGHT PERIOD
WEDNESDAY INTO THURSDAY. THE QUESTION REMAINS...HOW QUICKLY WILL THE
COLDER AIR MOVE IN? GIVEN THE LATEST GUIDANCE...TEMPERATURES WILL
LIKELY REMAIN ABOVE FREEZING FOR MUCH OF THE AREA UNTIL AROUND 06Z.
SO HAVE PUSHED BACK THE TIMING OF WHEN THE RAIN WILL TRANSITION TO
FREEZING RAIN UNTIL AFTER 06Z. TEMPERATURES WILL CONTINUE TO COOL
ACROSS THE AREA...WITH THE TRANSITION OF RAIN TO FROZEN PRECIP
OCCURRING THROUGH 09Z. BY 09Z...AREAS ACROSS THE NORTHWEST WILL
LIKELY SEE A TRANSITION FROM FREEZING RAIN TO SLEET...WHILE THE
REMAINING HALF OF THE FORECAST AREA EXPERIENCES FREEZING RAIN.

THE DURATION OF FROZEN PRECIP...ALONG WITH THE FORECAST QPF WILL
STILL LEAD TO ABOUT 6 HOURS OF FREEZING RAIN FOR THE AREA. ICE
ACCUMULATION AMOUNTS OF UP TO A QUARTER OF AN INCH ARE
POSSIBLE...WITH THE GREATEST AMOUNT ACROSS THE NORTHWEST. THE
BIGGEST CHANGE FROM THE PREVIOUS FORECAST IS THE AMOUNT OF SNOW
ACCUMULATIONS. GIVEN THE LATER TIMING OF THE FREEZING
TEMPERATURES...MODELS AGREE THAT THE WARM NOSE ALOFT WILL BE SLOW TO
ERODE...THEREFORE FREEZING RAIN WILL CONTINUE TO BE THE DOMINANT
PRECIP TYPE THROUGH 12Z. AFTER 12Z ON THURSDAY...ENOUGH MOISTURE
WILL BE LEFT IN PLACE TO WARRANT LIGHT QPF AMOUNTS...AND THE ENTIRE
VERTICAL TEMPERATURE PROFILE FINALLY DROPS BELOW FREEZING...SO THERE
WILL BE A FEW LINGERING SNOW SHOWERS. MOST LOCATIONS WILL RECEIVE
ONLY A DUSTING OF SNOW...HOWEVER LOCATIONS ACROSS THE CENTRAL
PORTION OF THE FORECAST AREA MAY SEE UP TO HALF AN INCH.

HIGH PRESSURE WILL BUILD IN BEHIND THE FRONT ON THURSDAY...WITH HIGH
TEMPERATURES ONLY REACHING INTO THE LOWER 30S. A DRY FORECAST IS IN
STORE FOR THE EXTENDED...WITH ONLY SCATTERED SHOWERS POSSIBLE TOWARD
THE LATTER PART OF THE FORECAST PERIOD.

73

&&

.AVIATION...
FOR 12Z TAFS...IFR STRATUS CIGS ARND 600 FT PREVAIL AT THE MSL/HSV
TERMINALS THIS MORNING...WITH VSBY RANGING FROM 2-6 SM. EXPECT
THESE CONDS TO CONTINUE THRU 03/17Z...ALONG WITH A LGT SE FLOW AND
PATCHY -DZ. WARM FRONT WILL LIFT NWD LATE THIS MORNING...WITH A MINOR
IMPROVEMENT IN CIGS BUT A MORE NOTICEABLE IMPROVEMENT IN VSBY AS
WINDS INCREASE FROM THE SSE. SHRA WILL BE PSBL THIS AFTN...BUT SCT
NATURE OF COVERAGE ONLY WARRANTS A VCSH ATTM. STRONGER SSW FLOW OF
10-15 KTS WILL DEVELOP BY 04/02Z AND LEAD TO A MORE WIDESPREAD
COVERAGE OF SHRA...WITH TEMPO INCLUDED BTWN 04/02-06Z. DESPITE THE
ELEVATED SSW FLOW...PREVAILING MVFR VSBY IS EXPECTED BTWN 08-12Z
ALONG WITH A CONTINUATION OF IFR CIGS ARND 600 FT.

70/DD

&&

.HUN WATCHES/WARNINGS/ADVISORIES...
AL...NONE.
TN...NONE.

&&

$$

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



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