National Weather Service National Headquarters

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

000
FXUS64 KHUN 101141 AAA
AFDHUN

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE HUNTSVILLE AL
541 AM CST WED FEB 10 2010

.UPDATE...
UPDATED FOR 12Z AVIATION DISCUSSION.

&&

.AVIATION.../12Z TAFS/
BRIEF MVFR CEILINGS CAN BE EXPECTED AT BOTH KMSL AND KHSV THROUGH
ROUGHLY 14Z. DECIDED TO INCLUDE -SN TO ACCOUNT FOR SOME SNOW
FLURRIES THIS MORNING AT KHSV...ALTHOUGH VISIBILITIES WILL NOT BE
IMPACTED DUE TO THE -SN. VFR CONDITIONS WILL THEN DEVELOP WITH
BKN-OVC CEILINGS BETWEEN 3500-5000 FEET EXPECTED TODAY. NORTHWEST
WINDS WITH GUSTS UP TO 25 KTS WILL BE POSSIBLE BUT WILL DECREASE
LESS THAN 7 KTS SUSTAINED AFTER 00Z.

&&

.DISCUSSION... /ISSUED 337 AM CST WED FEB 10 2010/

SHORT TERM (TODAY THRU SATURDAY)...
A COMPLEX WX PATTERN IS ONCE AGAIN TAKING SHAPE ACROSS THE CNTRL
TN VALLEY AREA THIS EARLY MORNING. AN UPPER LOW FEATURE OVER THE
OH VALLEY CONTINUES TO GRADUALLY SHIFT EWD TOWARD THE MID ATLANTIC
BASIN...AS WEAK EMBEDDED DISTURBANCES/WAVES ALOFT TRAVERSE EWD
UNDERCUTTING THE TROUGH PATTERN. THIS IS NOT ONLY ALLOWING
CONTINUED CAA INTO THE REGION...BUT IS ALSO PROVIDING FOR SOME
ISOLATED FLURRIES/LIGHT SNOW SHOWERS ACROSS THE EXTREME PORTIONS
OF NE AL...ALTHOUGH THESE LIGHT SHOWERS SHOULD COME TO AN END
LATER THIS MORNING WITH THE EXITING UPPER LOW. CONDITIONS THOUGH
SHOULD REMAIN QUITE COLD...ESPECIALLY WITH BREEZY SFC WINDS OUT OF
THE NW PERSISTING THROUGH THE AFTERNOON HRS. CAA ALSO LOOKS TO
CONTINUE INTO THE EVENING/OVERNIGHT HRS AS WEAK HIGH PRESSURE
SETTLES INTO THE LOWER/MID MS VALLEY LATER TODAY.

OVERALL TEMPS MAY WARM A FEW DEGREES GOING INTO THU AS THE SFC HIGH
CONTINUES TO WEAKEN AS IT GRADUALLY MOVES TOWARD THE E. NOT XPCTING
MUCH IN THE WAY OF ANY CLOUDS EXITING THE AREA AS A PREDOM ZONAL
FLOW ALOFT PREVAILS ACROSS THE SE REGION INTO FRI.

THE FORECAST PACKAGE THEN BECOMES A BIT OF A CHALLENGE HEADING INTO
THE WEEKEND PERIOD. THE LATEST GLOBAL MODELS REMAIN CONSISTENT WITH
SOME TYPE OF LOW PRESSURE AREA DEVELOPING IN THE WRN GULF DURING THE
LATE THU/EARLY FRI PERIOD. THE MODELS THEN BECOME SOMEWHAT DIVERGENT
WITH THE TRACK OF THIS SYSTEM ON FRI. HAVE OPTED TO USE A BLEND OF
THE 00Z NAM/ECMWF WITH THE HANDLING OF THIS FEATURE FRI AND SAT.
THIS WOULD BASICALLY HAVE THE LOW PRESSURE CENTER MOVING EWD ALONG
THE CNTRL GULF COAST FRI BEFORE EXITING INTO THE SRN ATLANTIC SAT.
THIS IS BECOMING QUITE THE POPULAR TRACK FOR GULF LOWS THIS WINTER
WITH MOISTURE ADVECTING NWD AHEAD OF THE SFC LOW. WITH A POLAR AIR
MASS FAIRLY ENTRENCHED ACROSS THE AREA...ANY PRECIP THAT DEVELOPS
ALMOST CERTAINLY WOULD BE ALL SNOW...BEGINNING WITH THE OVERNIGHT
HRS THU...AND THEN PROGRESSING FROM W TO E THROUGH FRI...BEFORE
TAPERING OFF FRI EVENING. QPF AMOUNTS THIS FAR N ARE NOT THAT HIGH
THUS FAR...LESS THAN 1/4 OF AN INCH. THIS TRANSLATES TO APPROX 1/2
TO 1 INCH OF SNOW ACCUMULATION...WITH THE HIGHER AMOUNTS SLATED FOR
THE SRN AREAS...OR MORE IN LINE WITH THE AXIS OF MOISTURE INFLOW.

THERE IS SOME UNCERTAINTY WITH THE ORIGIN AND TRACK OF THE SFC LOW
AND THE STRENGTH OF THE MOISTURE RETURN GIVEN THIS IS CLOSE TO 72
HRS OUT AND THERE IS SOME MODEL DISCREPANCY. HOPEFULLY FUTURE MODEL
RUNS WILL BECOME A BIT MORE CONSISTENT WITH THE TIMING AND PLACEMENT
OF THIS NEXT UPCOMING WINTER EVENT. 09

LONG TERM (SUNDAY THRU WEDNESDAY)...
A POTENT UPPER LEVEL LOW WILL DIVE SOUTHEAST ACROSS THE
MISSISSIPPI RIVER VALLEY ON SUNDAY AS A SURFACE LOW PRESSURE
SYSTEM AND ASSOCIATED COLD FRONT APPROACH THE AREA. WITH ENOUGH
MOISTURE AVAILABLE...LIGHT PRECIPITATION SHOULD BEGIN BY DAYBREAK
ACROSS NORTHWEST ALABAMA AND SPREAD EAST ACROSS THE TENNESSEE
VALLEY ON SUNDAY. AT THIS TIME...IT APPEARS TEMPERATURES WILL BE
BELOW FREEZING DURING THE MORNING HOURS TO WARRANT SNOW ESPECIALLY
ACROSS NORTHWEST ALABAMA. THE QUESTION REMAINS HOW WARM
TEMPERATURES WILL GET ON SUNDAY AFTERNOON WITH PRECIPITATION
FALLING CAUSING EVAPORATIVE COOLING. WITH THAT SAID...CONTINUED A
RAIN/SNOW MIX FOR SUNDAY AFTERNOON FOR THE ENTIRE AREA...ALTHOUGH
CONFIDENCE REMAINS LOW ON WHETHER TEMPERATURES WILL BE COLD ENOUGH
FOR ALL SNOW. LUCKILY...PRECIPITATION AMOUNTS SHOULD REMAIN LIGHT
WITH ROUGHLY A TENTH OF AN INCH IN QPF ADVERTISED.

BY SUNDAY NIGHT...THE ABOVE MENTIONED UPPER LOW WILL QUICKLY MOVE
NORTHEAST AS A LONGWAVE UPPER TROUGH SETTLES OVER THE AREA.  MOSTLY
CLOUDY SKIES WILL CONTINUE SUNDAY NIGHT WITH A FEW SNOW FLURRIES
POSSIBLE OVERNIGHT.  A CONTINUED COLD PATTERN WILL REMAIN ON MONDAY
WITH LOWS IN THE LOW TO MID 20S AND HIGHS IN THE MID TO UPPER 30S.
HIGH PRESSURE BEGINS TO BUILD OVER THE REGION ON TUESDAY AS
TEMPERATURES REMAIN WELL BELOW NORMAL. PERIODS OF CLOUDINESS CAN BE
EXPECTED MID WEEK AS SEVERAL MOISTURE STARVED UPPER LEVEL
DISTURBANCES MOVE ACROSS THE AREA. KNS

&&

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

$$

AVIATION...KNS
DISCUSSION...09/KNS