Area Forecast Discussion
Issued by NWS Huntsville, AL

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000
FXUS64 KHUN 170324 AAB
AFDHUN

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE HUNTSVILLE AL
1024 PM CDT TUE SEP 16 2014

.UPDATE...
EVENING UPDATE. ADJUSTED CLOUD COVER AND ADDED IN PATCHY VALLEY FOG.

&&

.DISCUSSION...
INFLUENCE OF THE SFC HIGH PRESSURE OVER THE GREAT LAKES WILL START TO
TAKE PLACE TOMORROW. SFC WINDS ARE NORTHERLY BEHIND THE COLD FRONT
THAT MOVED THROUGH AND NOW DOWN BY MONTGOMERY/AUBURN. ALL SHOWERS
AND THUNDERSTORMS HAVE DIMINISHED ACROSS THE TN VALLEY THIS EVENING.

THE WIND SHIFT FOR THE COLD FRONT MAY BE FARTHER SOUTH...BUT THE
TEMP CHANGE IS STILL IN THE TN VALLEY. LOOKING FOR TEMPS TO GET DOWN
INTO THE LOWER 60S IN AL TO UPPER 50S IN SOUTHERN MIDDLE TN TONIGHT.
CLOUD COVER WILL BE A FACTOR IN THE TEMPS AND ALSO IN THE POTENTIAL
FOR FOG DEVELOPMENT AS WELL. ONLY A FEW LOCATIONS RECEIVED RAINFALL
TODAY BUT RESIDUAL MOISTURE AND COOLING TEMPS WILL AID IN PATCHY
VALLEY FOG DEVELOPMENT TONIGHT IF CLOUD COVER COOPERATES. ADJUSTED
CLOUD COVER FOR TONIGHT INTO TOMORROW MORNING. SATELLITES SHOWED THE
WESTERN ZONES DECREASING IN CLOUD COVER AND SOUNDINGS HAVE DRIED OUT
A LITTLE SO DID NOT KEEP THE OVC SKIES GOING INTO THE MORNING HOURS.

JMS

&&

.AVIATION...
/ISSUED 638 PM CDT TUE SEP 16 2014/
FOR 00Z TAFS...SHOWERS AND THUNDERSTORMS SHOULD REMAIN SOUTH OF THE
TAF SITES THIS EVENING. VFR CONDITIONS WILL PREVAIL UNTIL CLOUD
COVER FILLS BACK IN FROM THE NW PROVIDING MFVR CONDITIONS OVERNIGHT.
DRIER AIR WILL MOVE IN TOMORROW AND VFR CONDITIONS WILL RETURN
TOWARDS THE LATE MORNING HOURS.

JMS

&&

.PREV DISCUSSION...
/ISSUED 151 PM CDT TUE SEP 16 2014/
TEMPS ARE EXCEEDING EXPECTATIONS JUST AHEAD OF THE ADVANCING
ANAFRONT WITH READINGS IN THE M-U80S. A SHARP 15-20 DEGREE DROP
EXISTS ACROSS THE FRONT IN NC/NW TN. THUS FAR, SHRA/TSRA ACTIVITY
HAS YET TO DEVELOP ALONG THE FRONT IN THE WARM SECTOR. IF ANYTHING,
WE COULD SEE A FEW POST FRONTAL SHRA, BUT EXPECT THIS TO BE LIMITED.
THE BIG QUESTION MARK WILL BE LOW CLOUD COVER AND PSBL DRIZZLE/FOG
LATER TONIGHT INTO WEDNESDAY. AN EXPANSIVE STRATUS DECK WAS FOUND
BEHIND THE FRONT SPANNING THE OH VALLEY. SOME OF THIS HAS BECOME A
MORE CELLULAR SC LAYER, BUT EXPECT AT LEAST SOME STRATUS TO REDEVELOP
TONIGHT PER NAM LOW LEVEL RH PROGS. THESE CLOUDS WILL TEND TO ERODE
FROM NE-SW ON WEDNESDAY. A STRONGER SHORTWAVE DROPS SE IN NWLY FLOW
ALOFT THRU THE OH AND UPPER TN VALLEY WED NIGHT. AT THE SAME TIME, A
THERMAL AND MOISTURE GRADIENT WILL BECOME ESTABLISHED FROM THE
CENTRAL PLAINS SE INTO MID SOUTH/LWR MS VALLEY LASTING INTO THURSDAY.
CLUSTERS OF CONVECTION, MUCH OF IT ELEVATED, WILL SPAN THIS GRADIENT
AND LIKELY JUST MISSING OUR WESTERN COUNTIES. DRIER E-NELY FLOW WILL
PERSIST OVER OUR AREA AS STRONG HIGH PRESSURE BUILDS INTO THE GREAT
LAKES AND APPALACHIANS. BY THIS WEEKEND, THE HIGH WILL PUSH INTO NEW
ENGLAND WITH A RIDGE AXIS STILL PRESENT THRU THE SPINE OF THE
APPALACHIANS. THIS WILL ONCE AGAIN FAVOR MORNING VALLEY FOG
DEVELOPMENT, PARTICULARLY IN OUR EASTERN VALLEYS. WILL NOT CARRY IN
THE FORECAST JUST YET, BUT IT MAY NEED TO BE ADDED IN FUTURE UPDATES.

DUE TO LACK OF INSTABILITY OR STRONG FORCING, WE HAVE REMOVED TSRA
FROM DAY 6 WITH THE NEXT COLD FRONT. THERE REMAINS RATHER
SIGNIFICANT DIFFERENCES IN THE MEDIUM RANGE MODELS (GFS, ECMWF, AND
CANADIAN) WRT STRONG AMPLIFICATION AND PLACEMENT OF TROF/RIDGES
ACROSS OUR PORTION OF THE NH. WILL LEAVE DAY 7 ALONE AND HOPEFULLY
SEE BETTER AGREEMENT FOR UPCOMING FORECASTS THIS WEEK.

AK

&&

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

$$

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


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