Area Forecast Discussion
Issued by NWS Huntsville, AL

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000
FXUS64 KHUN 230929
AFDHUN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HUNTSVILLE AL
429 AM CDT WED JUL 23 2014

.DISCUSSION...
EARLY MORNING ANALYSIS ACROSS NORTH AMERICA AND ADJACENT WATERS
SHOWS MARKED AMPLIFICATION OF THE LONG WAVE PATTERN MAINLY ACROSS
CANADA WHILE AN IMPRESSIVE 600 DAM 500MB RIDGE DOMINATES ACROSS A
LARGE PORTION OF THE WEST/CENTRAL CONUS. A CLOSED MID-LVL LOW THAT
BROUGHT SOME SHOWERS/TSTMS TO THE AREA OVER THE PAST COUPLE OF DAYS
CONTINUES TO MEANDER SLOWLY WWRD ALONG THE GULF COAST. A SHORT
WAVELENGTH BUT HIGH AMPLITUDE TROUGH IS LOCATED JUST OFF THE
US/CANADIAN WEST COAST. THIS FEATURE WILL FIGURE MORE INTO OUR
SENSIBLE WEATHER NEXT WEEK. HERE IN THE TN VALLEY THIS
MORNING...EARLY MORNING TEMPS ARE MAINLY IN THE 70S...ALTHOUGH A
COUPLE OF SPOTS IN THE REGION HAD DROPPED INTO THE UPR 60S. MULTI-
SPECTRAL SAT IMAGERY AND SOME SFC OBS INDICATE THE DEVELOPMENT OF FOG
MAINLY IN THE EASTERN VALLEYS OF JACKSON AND DEKALB COUNTIES. AN SPS
HAS BEEN ISSUED SO FAR TO ADDRESS THIS WEATHER CONCERN. FURTHER
REDUCTIONS IN VIS THIS MORNING MAY NECESSITATE A DENSE FOG
ADVISORY...FOR WHICH WE WILL BE WATCHING. WITH THAT SAID...LET`S GET
TO THE FCST DETAILS.

THE AFORE-MENTIONED FOG IN THE EASTERN VALLEYS IS LIKELY TO REMAIN
THROUGH THE MORNING COMMUTE ALTHOUGH WIDESPREAD DENSE FOG IS NOT
ANTICIPATED. THIS WAS INTRODUCED INTO THE FCST FOR THE MORNING HOURS
BUT SHOULD DISSIPATE BY 8-9 AM THIS MORNING WITH THE ADVENT OF
DEEPER MIXING. MID-LVL MOISTURE HAS ADVECTED EWRD THIS MORNING AND
CLOUD DEVELOPMENT AROUND 7-9 KFT BELIES THE PRESENCE OF SHEARED MID-
LVL VORTICITY AS ANALYZED BY REGIONAL/GLOBAL MODELS. THIS IS AN
EXTENSION OF THE CLOSED UPR LOW TO OUR SOUTH. AS A TROUGH DIGS
SOUTHWARD INTO THE OH/TN VALLEY REGION THROUGH THE DAY, THIS SHEARED
PORTION OF THE CLOSED UPR LOW WILL BE MAINTAINED ACROSS THE AREA.
THIS SHOULD RESULT IN SUFFICIENT INSTABILITY/LIFT FOR THE
DEVELOPMENT OF SCTD SHRA/TSTMS IN THE AREA TODAY. CAPE VALUES ARE
MARGINAL AND SHEAR IS NOT SUPPORTIVE OF ORGANIZED ACTIVITY. SHEARING
WINDS ALOFT MAY ACTUALLY ACT TO LIMIT VERTICAL GROWTH, SO
SIGNIFICANT STORMS ARE NOT ANTICIPATED.

A WEAKENING COLD FRONT IS STILL ANTICIPATED TO MOVE INTO THE REGION
LATE TONIGHT AND EXIT SOMETIME TOMORROW. CHANCES FOR SHOWERS/TSTMS
WILL INCREASE MAINLY AFTER MIDNIGHT AND FOR TOMORROW. THE ADDED LIFT
ALONG THE FRONT MAY RESULT IN GREATER COVERAGE OF SHOWERS BUT
INSTABILITY WILL BE SOMEWHAT LIMITED OVERNIGHT. THE DEW POINT
GRADIENT WILL LIKELY LINGER BEHIND THE FRONT SUFFICIENTLY TO ALLOW
FOR THE DEVELOPMENT OF SHOWERS AND STORMS IN THE AREA AGAIN
TOMORROW...WITH THE BEST CHANCES IN THE SOUTH. THROUGHOUT TONIGHT
AND TOMORROW...SHEAR WILL BE LIMITED AND NOT SUPPORTIVE OF STRONG
STORM ORGANIZATION. NEVERTHELESS, INSTABILITY WILL BE STRONG ENOUGH
FOR SOME GUSTY WINDS WITH ANY HEAVIER CELLS. RESPECTABLE PW`S AROUND
1.8-1.9 INCHES WILL ALLOW FOR CELLS WITH HVY RAIN...BUT ANY FLASH
FLOODING WILL LIKELY BE VERY LOCALIZED.

DRIER AND SLIGHTLY COOLER AIR WILL ENTER THE REGION FOR THURS WITH
HIGHS MAINLY IN THE LOW/MID 80S EXPECTED. HOWEVER, THE COOLER
AIRMASS WILL BE QUITE BRIEF AS THE WESTERN RIDGE EXPANDS INTO
PORTIONS OF THE EASTERN CONUS DURING THE WEEKEND.  850 MB TEMPS
REACH A MAX AROUND 22C ON SAT/SUN WHICH WOULD TRANSLATE INTO SFC
TEMPS IN THE LOW/MID 90S FOR MOST OF THE AREA. DEW POINT VALUES WILL
CLIMB INTO THE 70S FOR MUCH OF THE AREA DURING THE WEEKEND AS
SOUTHERLY FLOW RETURNS TO THE REGION. THIS WILL RESULT IN HEAT
INDICES OVER 100F AT SOME LOCATIONS DURING THE
WEEKEND...PARTICULARLY ON SUNDAY WHEN VALUES MAY BE THE HIGHEST.

CONFIDENCE IS HIGH THAT AN INCREASINGLY AMPLIFIED PATTERN WILL
DEVELOP ACROSS THE CONUS DURING NEXT WEEK. THE STRONG SHORT WAVE
ALONG THE BASE OF THE EAST PAC TROUGH WILL EJECT EWRD ACROSS CANADA
DURING THE WEEKEND...THEN ROUND THE APEX OF THE RIDGE AND HELP TO
CARVE A SIGNIFICANT TROUGH IN THE EASTERN CONUS NEXT WEEK. THE
ATTENDANT SFC COLD FRONT IS CURRENTLY EXPECTED TO CROSS THE AREA
SOMETIME LATE SUNDAY NIGHT OR MONDAY MORNING. NEVERTHELESS, DUE TO
THE ADDED SYNOPTIC FORCING AND MOISTURE POOLING AND INSTABILITY
AHEAD/ALONG THE FRONT...SHOWER/TSTM CHANCES WILL INCREASE. THE
AIRMASS MOVING INTO THE REGION BEHIND THE FRONTAL BOUNDARY WILL BE A
MIX OF N PAC AND CANADIAN CONTINENTAL AIR. STILL, LOW DEW POINT TEMPS
IN THE 50S APPEAR INCREASINGLY PROBABLE FOR THE AREA ALONG WITH TEMPS
MORE CHARACTERISTIC OF MID/LATE SEPTEMBER.

KDW

&&

.AVIATION...
/ISSUED 1202 AM CDT WED JUL 23 2014/
FOR 06Z TAFS...PATCHY FOG IS POSSIBLE AT BOTH KMSL/KHSV BY DAYBREAK,
BUT WILL QUICKLY ERODE BY 14Z. SHOWERS AND STORMS WILL DEVELOP AGAIN
TOMORROW AFTN, WITH MVFR CONDS EXPECTED IN ANY TSTORM ACTIVITY.
CONVECTION WOULD DISSIPATE BY 02Z TOMORROW NIGHT.

12

&&

.PRELIMINARY POINT TEMPS/POPS...
HUNTSVILLE    91  72  84  66 /  50  50  60  10
SHOALS        91  72  85  65 /  40  50  40  10
VINEMONT      90  70  84  67 /  50  40  60  10
FAYETTEVILLE  89  70  82  64 /  50  60  40  10
ALBERTVILLE   87  73  84  68 /  50  40  60  10
FORT PAYNE    87  68  84  65 /  50  40  60  10

&&

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

$$

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



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