« Back
NWS Peachtree City, Ga » Text Product » HUN Area Forecast Discussion


Printer-friendly Version
Current Version              Previous Versions:   1  2  3  4  5  6  7  8  9  

Area Forecast Discussion

673
FXUS64 KHUN 202327
AFDHUN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HUNTSVILLE AL
627 PM CDT SUN APR 20 2014

.UPDATE...
FOR 00Z TAFS

&&

.SYNOPSIS...
/ISSUED 212 PM CDT SUN APR 20 2014/

WHAT A BEAUTIFUL EASTER SUNDAY TODAY! WE ARE CURRENTLY UNDER THE
INFLUENCE OF A SHORTWAVE RIDGE IN BETWEEN A SHORTWAVE TROUGH (WEST)
AND A QUASI-CUTOFF LOW OFF THE CAROLINA COASTLINE. THIS HAS MOSTLY
SUNNY CONDITIONS WITH DAYTIME HIGHS IN THE MID TO UPPER 70S. THE
MID-LEVEL SHORTWAVE TROUGH TO OUR WEST HAS THE POTENTIAL TO CAUSE
SEVERE WEATHER OVER W TX AND BRING SHOWERS AND NON-SEVERE STORMS TO
OUR AREA MONDAY NIGHT INTO TUESDAY. FURTHER WEST, A RIDGE IS BUILDING
OVER THE ROCKIES WHILE A VORTEX OFF THE GULF OF ALASKA IS MOVING
ONSHORE OVER CENTRAL BRITISH COLUMBIA. REGARDING THE UPPER FLOW
PATTERN, THE SPLIT UPPER FLOW WILL SLOWLY TRANSITION TO AN AMPLIFIED
TROUGH PATTERN BY THE END OF THE FORECAST PERIOD. ALL OF THESE
FEATURES WILL HAVE AN IMPACT ON OUR WEATHER OVER THE COMING DAYS. SO,
LET`S DELVE INTO THE DETAILS...

SL.77

&&

.SHORT TERM (TONIGHT THROUGH TUESDAY NIGHT)...
/ISSUED 212 PM CDT SUN APR 20 2014/

CIRRUS CLOUDS FROM THE ONCOMING MID-LEVEL SHORTWAVE TROUGH HAVE
ALREADY BEGUN TO MOVE ACROSS THE AREA AND THESE SHOULD CONTINUE
TO ADVECT THROUGH THE OVERNIGHT HOURS. LIGHT SOUTHERLY SFC WINDS AND
THE THIN CIRRUS WILL MEAN RADIATIONAL COOLING SHOULD DOMINATE WITH
OVERNIGHT LOWS IN THE UPPER 40S TO NEAR 50.

THE MID-LEVEL SHORTWAVE TROUGH IS EXPECTED TO MOVE SOUTHEAST
EFFECTIVELY ACTING TO DAMPEN THE RIDGE SETUP OVER THE SOUTHEAST. THE
RESULT WILL BE A DE-AMPLIFIED AND SHEARED SHORTWAVE OVERSPREADING
THE AREA MONDAY NIGHT INTO TUESDAY. DID KEEP THE MENTION OF SHOWERS
STARTING MONDAY MORNING OVER FAR NW AL AND EXTENDING AREAWIDE MONDAY
AFTERNOON, WITH SUBTLE UNDULATIONS/PVA MOVING WITHIN THE MID LEVEL
FLOW. FORECAST SOUNDINGS DEPICT A CAP BTWN 800-750 HPA THAT WILL
LIKELY BE STRONG ENOUGH TO KEEP DEEP CONVECTION FROM DEVELOPING.
THERE IS STILL UNCERTAINTY WITH THE INSTABILITY PROFILE AND WENT
AHEAD AND ADDED ISOLATED THUNDERSTORMS OVER FAR NW AL ON MONDAY
AFTERNOON. OTHERWISE, THE CAP WILL ERODE AREAWIDE AND INSTABILITY
WILL RISE MONDAY NIGHT INTO TUESDAY. THE GREATER AMOUNT OF
INSTABILITY SHOWN BY BOTH PLAN VIEW AND PROFILE FORECASTS SHOW
TUESDAY AFTERNOON AS THE PRIME TIME DUE TO DAYTIME HEATING. BY
TUESDAY AFTERNOON, THE FORECAST SOUNDINGS DEPICT AN INSTABILITY
PROFILE THAT IS MORE SKINNY IN NATURE WITH VERY WEAK WIND SHEAR, AND
INVERTED V LOW-LEVEL T/DEWPOINT TRACE. THIS WILL TRANSLATE TO SLOW
MOVING AND PULSE-LIKE NATURE STORMS WITH SMALL HAIL AND GUSTY WINDS
(DUE TO MICROBURST POTENTIAL) ON TUESDAY AFTERNOON, AFTER WHAT IS
LEFT OF THE TROUGH MOVES SOUTHEAST. A WEAK W-E ORIENTED COLD FRONT
SHOULD THEN CROSS OVER THE REGION LATE ON TUESDAY AFTERNOON BRINGING
A SWIFT END TO THE SHOWERS/THUNDERSTORM ACTIVITY. NEEDLESS TO SAY,
THE TEMPERATURE FORECAST FOR MONDAY NIGHT AND TUESDAY HAS BEEN A
LITTLE CHALLENGING WITH WEAK WAA AND BREAKS IN THE CLOUDS POSSIBLE
TUESDAY MORNING. SO, CHANGES IN THE TEMP FORECAST ARE LIKELY WITH
UPCOMING FORECAST PACKAGE CHANGES.

OVERNIGHT LOWS WILL BE COOLER TUESDAY NIGHT AS LIGHT SFC NW FLOW
SENDS TEMPERATURES INTO THE MID 40S FOR OVERNIGHT LOWS.

.LONG TERM (WEDNESDAY THROUGH SUNDAY)...

DUE TO THE MODIFIED COOLER AIRMASS SETUP OVER THE REGION ALONG WITH
WEAK SFC NW FLOW, BY WEDNESDAY, DAYTIME HEATING WILL RESULT IN TEMPS
RISING INTO THE MID 70S BY THE AFTERNOON. IN THE MID-UPPER LEVELS, A
RIDGE WILL BE BUILDING OVER THE SOUTHEAST ON WEDNESDAY AND THURSDAY.
THE SOUTHEAST WILL BRIEFLY BE ON THE EASTERN FLANK OF THE RIDGE, BUT
AS THE RIDGE MOVES EAST FROM THE SOUTHERN PLAINS, THE SOUTHEAST WILL
BE WITHIN SW FLOW ALOFT TRANSLATING TO LOW 80S AS HIGHS BY THURSDAY
AFTERNOON.

THIS WHERE THE PREVIOUSLY MENTIONED GULF OF ALASKA VORTEX WILL
BECOME IMPORTANT FOR OUR AREA. BY THIS TIME, THAT VORTEX WILL HAVE
INDUCED SFC CYCLOGENESIS OVER EAST BRITISH COLUMBIA/ALBERTA AND
MOVED EAST ALONG THE US/CANADIAN BORDER. A COUPLE OF MID-LEVEL
SHORTWAVES WILL BE SPINNING AROUND IT OR MERGE WITH THE MAIN VORTEX
BY WEDNESDAY NIGHT. THE PRIMARY SFC LOW LOOKS TO OCCLUDE WITH A
SECONDARY SFC LOW DEVELOPING OVER THE CORN BELT REGION BY THURSDAY
AFTERNOON. FOR THE FIRST TIME, THE ECMWF/GFS/CANADIAN ARE ALL
BEGINNING TO SHOW A NEGATIVE TILT TO THE SHORTWAVE MOVING ACROSS
CORN BELT REGION WITHIN THE PARENT VORTEX. THIS COULD MEAN SEVERE
WEATHER OVER THAT REGION. HOWEVER, THE MAIN IMPACT HERE LOOKS TO BE
THE SLOW TRAILING COLD FRONT MOVING E/SE ACROSS THE MS RIVER AND THEN
TN VALLEY BY FRIDAY/FRIDAY NIGHT. THE MODELS CONTINUE TO HAVE
DIFFICULTY WITH THE STRENGTH OF THE RIDGE OVER THE EASTERN HALF OF
THE COUNTRY WHICH IS TO BE EXPECTED IN A TRANSITION PATTERN. THE
ECMWF APPEARS TO BE THE MOST CONSISTENT WITH THE PROGRESSION OF THIS
SYSTEM. SO, FOR NOW, HAVE KEPT A CHANCE OF THUNDERSTORMS IN THE
FORECAST FOR BOTH FRIDAY/FRIDAY NIGHT. MORE DETAILS SHOULD BE
FORTHCOMING WITH SUBSEQUENT MODEL RUNS. HAVE LEFT SCHC OF STORMS FOR
SUNDAY WITH SOME MODELS INDICATING ANOTHER SYSTEM APPROACHING THE
AREA. OTHERWISE, LEFT SLIGHTLY WARMER THAN AVERAGE DAYTIME
HIGHS/OVERNIGHT LOWS FOR THE EXTENDED.

SL.77

&&

.AVIATION...
FOR 00Z TAFS...AN UPPER RIDGE WILL CONTINUE OVER THE CWA FOR
TONIGHT. BY MONDAY AFTN THE RIDGE WILL MOVE EAST OF THE TN VALLEY
FOLLOWED BY AN UPPER TROF/CDFNT. THIS COMBO WILL INCREASE THE CHC OF
SHRA/TSRA OVER THE TAF SITES. HOWEVER WILL NOT INCLUDE PCPN IN TAFS
ATTM SINCE IT LOOKS LIKE THE BEST CHC OF PCPN WILL BE AFTER 00Z
MONDAY NIGHT. OTHERWISE VFR CONDITIONS ARE EXPECTED THRU THE FCST
PERIOD.

07

&&

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

$$

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



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.