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000
FXUS64 KHUN 232321 AAA
AFDHUN

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE HUNTSVILLE AL
621 PM CDT THU MAY 23 2013

.UPDATE...
FOR 00Z TAFS

&&

.DISCUSSION...
/ISSUED 225 PM CDT THU MAY 23 2013/
WATER VAPOR IMAGERY AND 500MB RAP ANALYSIS INDICATED AN OMEGA BLOCK
IN PLACE ACROSS THE CONUS THIS AFTERNOON, WITH UPPER LOWS IN PLACE
OVER THE EAST/WEST COASTS, AND RIDGING ALOFT BETWEEN THE TWO OVER
THE CENTRAL PLAINS. CLOSER TO HOME AND AT THE SFC, A COLD FRONT WAS
IN THE PROCESS OF PUSHING THROUGH THE CWA AS OF THIS WRITING, WITH
NORTHWEST WINDS INCREASING ALONG/AHEAD OF THE BOUNDARY, AND DEWPOINTS
FALLING IN ITS WAKE.

AS A RESULT, FOR THIS EVENING/TONIGHT, SHOWERS AND STORMS WILL
CONTINUE DEVELOPING OVER EASTERN TN AHEAD OF THE FRONT. THIS
ACTIVITY IS NOT EXPECTED TO IMPACT OUR CWA, BUT SILENT POPS WERE
TAPERED SLIGHTLY HIGHER IN THE NORTHEASTERN LOCATIONS AS A RESULT.

THE BIGGER STORY FOR THE SHORT TERM WILL BE THE COOLER/DRIER
CONDITIONS IN PLACE IN THE WAKE OF THE DEPARTED FRONT. MORNING LOWS
TOMORROW WILL BE 5-10 DEGREES COOLER THAN NORMAL LOWS FOR THIS TIME
OF YEAR (NORMALLY IN THE LOWER 60S). HIGHS TOMORROW AFTERNOON WILL
FOLLOW SUIT, ONLY TOPPING OUT IN THE LOWER 70S IN MOST LOCATIONS,
WITH THE EXCEPTION OF THE UPPER 60S TO AROUND 70 DEGREES EXPECTED IN
SRN MIDDLE TN. NORMAL HIGHS FOR LATE MAY ARE IN THE LOWER 80S, SO BE
SURE TO ENJOY THE SLIGHTLY `COOLER` HIGHS OF ~70-75F WITH LOWER
HUMIDITY, BECAUSE THAT WILL DEFINITELY CHANGE AS WE GO THROUGH THE
REMAINDER OF THE FORECAST PERIOD.

AFTER THE COOLEST START TO THE FORECAST WITH MORNING LOWS IN THE
MIDDLE TO UPPER 40S SATURDAY MORNING, THE UPPER HIGH CURRENTLY IN
PLACE OVER MUCH OF THE CENTRAL CONUS THIS AFTN WILL SHIFT EASTWARD
THROUGH THE DAY, CONTINUING INTO THE EARLY PART OF NEXT WEEK.
TEMPERATURES WILL WARM A COUPLE OF DEGREES EACH DAY, WITH
TEMPERATURES APPROACHING THE 90-DEGREE MARK AGAIN BY THE END OF THE
WEEK.

IT IS AT THIS POINT, HOWEVER, THAT GLOBAL MODELS DIVERGE. THE GFS IS
BY FAR DRIER THAN THE ECMWF FOR THE EXTENDED, KEEPING ANY MCS
ACTIVITY THAT DEVELOPS TO THE NW WELL NORTH OF THE AREA (OVER THE OH
RIVER VALLEY). THE ECMWF, HOWEVER, IS MUCH STRONGER WITH THE UPPER
RIDGING IN PLACE, SLIGHTLY SHIFTING IT WESTWARD THROUGH THE PERIOD.
THIS WOULD SET UP NW FLOW OVER THE TN VALLEY, DIRECTING ANY MCS
ACTIVITY THAT DEVELOPS TOWARD THE CWA. AS A RESULT, WILL LEAVE THE
ISOLATED MENTION OF SHOWERS AND STORMS IN FOR THE FIRST PART OF NEXT
WEEK, BUT THESE CHANCES MAY NEED TO BE INCREASED. MODELS GENERALLY
DON`T PERFORM WELL IN NW FLOW (ESPECIALLY OVER THE TN VALLEY THIS
TIME OF YEAR), AND AS WE NEAR THE MONTH OF JUNE, THIS PATTERN IS
GENERALLY MORE FAVORED THAN THE OUTPUT OF THE CURRENT RUN OF THE GFS.
FOR NOW, WILL ONLY MAKE MINOR CHANGES TO THE FORECAST BEYOND THIS
POINT, BUT EITHER WAY, THE FORECAST LOOKS TO BE WARM AND DRY LATE IN
THE PERIOD, WITH HUMIDITY INCREASING THROUGH THE END OF NEXT WEEK.

12

&&

.AVIATION...
FOR 00Z TAFS...

VFR CONDITIONS AND LIGHTER WINDS ARE EXPECTED TO PREVAIL OVER THE
NEXT 6-7 HOURS WHEN A SFC COLD FRONT CROSSES THE REGION. LOW STRATUS
WILL ACCOMPANY THIS FRONT AND MAY RESULT IN CIGS DROPPING TO `ADDL
FUEL REQ` CONDITIONS BTWN 07-11Z, AND WINDS VEERING TO THE N/NE.
WINDS ARE EXPECTED TO INCREASE AFTER 14Z THROUGH THE REST OF THE
FORECAST PERIOD AS A SFC HIGH PRESSURE SYSTEM ADVECTS SOUTHWARD.

SL.77

&&

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

$$

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