National Weather Service National Headquarters

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

000
FXUS64 KHUN 150223 AAB
AFDHUN

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE HUNTSVILLE AL
923 PM CDT FRI JUN 14 2013

.UPDATE...
FEW CHANGES NEEDED TO THE FORECAST. RAISED THE HSV METRO MIN TEMP UP
A COUPLE DEGREES TO ACCOUNT FOR THE URBAN HEAT ISLAND.
&&

.DISCUSSION...
AFTER A "NORMAL" DAY TEMP-WISE, TEMPS ARE SLIDING INTO THE M60S-L70S.
SOME MOSTLY THIN CONVECTIVE DEBRIS CI CLOUDS ARE SPILLING SEWD INTO
THE REGION. MOST AREAS ARE EXPERIENCING CALM OR VERY LIGHT NELY FLOW.
THE ONLY ADJUSTMENT NEEDED FOR THE FORECAST WAS TO ACCOUNT FOR THE
HSV HEAT ISLAND A BIT MORE, SO RAISED MIN TEMPS (AND CORRESPONDING
HOURLY TEMPS) BY A COUPLE DEGREES. OTHERWISE, THE REST OF THE
FORECAST LOOKS IN FINE SHAPE.

AK

&&

.AVIATION...
/ISSUED 617 PM CDT FRI JUN 14 2013/
FOR 00Z TAFS... VFR CONDITIONS ARE FORECAST DURING THE NEXT 24 HOURS.
HIGH PRES WILL DRIFT EASTWARD FROM THE OHIO VALLEY ALLOWING SFC FLOW
TO TURN S-SELY ON SATURDAY. SCT CU WILL DEVELOP DURING THE DAY.

AK

&&

.PREV DISCUSSION...
/ISSUED 350 PM CDT FRI JUN 14 2013/
A STRONG NORTHWEST FLOW ALOFT CONTINUES ACROSS NORTHERN ALABAMA AND
SOUTHERN MIDDLE TENNESSEE THIS AFTERNOON...BETWEEN A MID-LEVEL HIGH
CENTERED OVER THE ARKLATEX AND A 500-MB SHORTWAVE TROUGH DIGGING
SOUTHEASTWARD OFF THE COAST OF NEW ENGLAND AND THE MID-ATLANTIC. THIS
REGIME -- WHICH ASSISTED IN PUSHING A STRONG COLD FRONT SOUTHWARD
ACROSS THE FORECAST AREA YESTERDAY -- HAS RESULTED IN A PERIOD OF
VERY PLEASANT LATE SPRING WEATHER...WITH DEWPOINTS IN THE MID 40S-MID
50S AND TEMPERATURES ONLY RISING INTO THE MID 80S AS OF THIS WRITING.
THE PLEASANT CONDITIONS ARE EXPECTED TO PERSIST THROUGH TONIGHT...
WITH A LIGHT EAST-NORTHEAST SURFACE WIND MAINTAINING THE ADVECTION OF
SLIGHTLY DRIER AIR INTO THE REGION. HOWEVER...THE PASSAGE OF A MID-
LEVEL WAVE IN THE NORTHWEST FLOW ALOFT MAY GENERATE SUFFICIENT MID
/HIGH-LEVEL CLOUDINESS OVERNIGHT TO PREVENT THE FULL EFFECTS OF
RADIATIONAL COOLING FROM BEING REALIZED...AND WILL FORECAST LOWS
GENERALLY IN THE UPPER 50S/LOWER 60S.

SHORT TERM MODELS AGREE THAT THE CENTER OF THE ARKLATEX MID-LEVEL
RIDGE WILL SHIFT SOUTHEASTWARD FROM TONIGHT THROUGH TOMORROW...
BECOMING CENTERED ACROSS THE NORTH CENTRAL GULF OF MEXICO BY SATURDAY
EVENING. THIS WILL OCCUR AS A WEAK UPPER LOW -- CURRENTLY LOCATED
ACROSS WEST TEXAS -- OPENS INTO AN AMPLIFIED WAVE AND LIFTS
NORTHEASTWARD ACROSS THE SOUTHERN PLAINS. STRONG SUBSIDENCE WARMING
TO THE NORTH OF THE MID-LEVEL RIDGE WILL ALLOW 850 MB TEMPERATURES TO
WARM AT LEAST A COUPLE OF DEGREES OVER VALUES FROM TODAY...AND THIS
COUPLED WITH MOSTLY SUNNY SKIES AND LIGHT SOUTHERLY RETURN FLOW WILL
FORCE HIGH TEMPERATURES INTO THE LOWER 90S ONCE AGAIN. MID-
TROPOSPHERIC WEST-SOUTHWESTERLY FLOW WILL INCREASE BY SATURDAY
NIGHT...INDUCED BY THE WEAKENING SOUTHERN PLAINS SHORTWAVE TROUGH
WHICH IS PROGGED TO EXTEND FROM THE MID-MISSISSIPPI VALLEY SOUTH-
SOUTHWESTWARD INTO EAST TEXAS BY SUNDAY MORNING. DEEP-LAYER MOISTURE
WILL BEGIN TO INCREASE IN THIS REGIME...BUT A LINGERING POCKET OF
SLIGHTLY DRIER AIR ACROSS THE NORTHEAST ZONES MAY STILL ALLOW LOWS ON
SUNDAY MORNING TO FALL INTO THE LOWER/MID 60S...WITH STRONGER WINDS
AND LOW-LEVEL MOISTURE RETURN EXPECTED TO KEEP LOWS IN THE UPPER 60S
ACROSS NORTHWEST ALABAMA. CHANCES FOR SHOWERS/THUNDERSTORMS WILL
INCREASE REGION-WIDE ON SUNDAY...AS THE WEAK MID-LEVEL SHORTWAVE
TROUGH ADVANCES EASTWARD ACROSS THE MISSISSIPPI VALLEY AND INTO THE
TENNESSEE VALLEY DURING THE LATE AFTERNOON. DESPITE THE WEAK NATURE
OF THE MID-LEVEL WAVE AND ASSOCIATED QG FORCING FOR UVM...
STRENGTHENING/VEERING FLOW IN THE SFC-700MB LAYER SHOULD PROVIDE
SUFFICIENT LARGE SCALE ASCENT TO GENERATE AT LEAST SCATTERED
SHOWERS/STORMS -- ESPECIALLY AS DEWPOINTS RISE INTO THE UPPER
60S/LOWER 70S AND PWATS INCREASE INTO THE 1.5-1.75 INCH RANGE. THIS
ACTIVITY WILL LIKELY PERSIST THROUGH THE NIGHT AS THE MID-LEVEL
DISTURBANCE TRACKS EASTWARD.

IT APPEARS AS IF A CLIMATOLOGICALLY-FAVORED WEST-NORTHWEST FLOW
REGIME WILL SET UP ACROSS THE CENTRAL TENNESSEE VALLEY EARLY NEXT
WEEK...AS THE REGION WILL REMAIN LOCATED BETWEEN A MID-LEVEL CYCLONE
PROGGED TO CUTOFF ACROSS QUEBEC AND THE PACIFIC SUBTROPICAL HIGH
WHICH IS FORECAST TO GRADUALLY BUILD NORTHEASTWARD INTO THE SOUTHERN
PLAINS. THIS PATTERN IS EXPECTED TO PERSIST FOR AT LEAST THE FIRST
HALF OF THE EXTENDED FORECAST PERIOD...WITH THE PASSAGE OF SEVERAL
MID-LEVEL VORTICITY MAXIMA AND PRESENCE OF A WEAK/ILL-DEFINED SURFACE
COLD FRONT SAGGING SOUTHWARD INTO THE AREA LEADING TO PERIODS OF RAIN
AND THUNDERSTORMS FROM MONDAY INTO TUESDAY. MEDIUM RANGE GUIDANCE
FROM THE GFS/ECMWF DOES INDICATE A FAIRLY PRONOUNCED MID-LEVEL WAVE
DIGGING SOUTHEASTWARD ACROSS THE CENTRAL PLAINS ON SUNDAY
NIGHT...WITH THIS FEATURE PERHAPS IMPACTING THE LOCAL AREA LATE
MONDAY OR MONDAY NIGHT. THE RISK OF ORGANIZED/SEVERE CONVECTION MAY
BE SLIGHTLY HIGHER DURING THIS PERIOD...AS MID-LEVEL FLOW
STRENGTHENS...BUT WILL SIMPLY MAINTAIN STRONG STORM WORDING IN THE
HWOHUN AT THIS TIME AS FORECAST DETAILS FOR THE MONDAY-TUESDAY
TIMEFRAME WILL BE STRONGLY INFLUENCED BY MESOSCALE IMPACTS. AS THE
WEAK COLD FRONT SHIFT SOUTHWARD ON TUESDAY...PRECIPITATION CHANCES
WILL LIKELY DIMINISH...BUT NORTHWEST FLOW ALOFT WILL CONTINUE FOR THE
REMAINDER OF THE FORECAST PERIOD WARRANTING A SLIGHT CHANCE POP
THROUGH THE END OF THE WEEK. THE COMBINATION OF MORE CLOUDS AND
SLIGHTLY COOLER TEMPERATURES WILL KEEP HEAT INDEX VALUES FROM RISING
TOO SIGNIFICANTLY...WITH MAXIMUM HEAT INDICES GENERALLY IN THE 90-95
DEGREE RANGE.

70/DD

&&

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

$$

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