Freeze Watch 1, NWS Mobile, AL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOBILE AL
1143 PM CST FRI NOV 20 2015

.DISCUSSION...UPDATED FOR LATEST AVIATION DISCUSSION BELOW.

&&

.AVIATION...
06Z ISSUANCE...VFR CONDITIONS THROUGH ABOUT 21.09Z FOLLOWED BY MVFR
CIGS AND VISIBILITIES THROUGH ABOUT 21.14Z...THEN MVFR CIGS THROUGH
21.18Z. INCREASING CLOUDS (INITIALLY HIGH LEVEL) AND MOISTURE IN THE
BOUNDARY LAYER EXPECTED TONIGHT AND EARLY SATURDAY AS A COLD FRONT
APPROACHES FROM THE WEST AND NORTHWEST. THE COLD FRONT IS STILL
EXPECTED TO MOVE EAST ACROSS THE REGION LATE SATURDAY AFTERNOON OR
SATURDAY EVENING. WINDS WILL CONTINUE FROM THE NORTHEAST AND EAST
THROUGH 21.18Z GRADUALLY VEERING TO THE NORTHWEST AND INCREASING
LATE SATURDAY AFTERNOON AND EVENING BEHIND THE FRONT. ONLY A SLIGHT
CHANCE FOR SHOWERS WITH THE FRONTAL PASSAGE SATURDAY AFTERNOON/EVENING...
WILL INDICATE VCSH IN TAFS. 12/DS

&&

.PREV DISCUSSION... /ISSUED 402 PM CST FRI NOV 20 2015/

NEAR TERM /NOW THROUGH SATURDAY/...

BROAD UPPER TROF CURRENTLY OVER MUCH OF THE CENTRAL PART OF THE
COUNTRY BEGINS TO DIG LATE TONIGHT AND EARLY SAT GENERALLY OVER THE
MID SECTION OF THE COUNTRY MOVING EASTWARD REACHING THE MID MS/TN
RIVER VALLEYS BY 00Z SUN. AHEAD OF THIS SYSTEM DEEPER MOISTURE
GENERALLY FROM THE W AND SW WEST BEGINS TO ADVECT EASTWARD ACROSS
THE LOWER MS RIVER VALLEY AND CENTRAL GULF STATES COUPLED WITH A
VERY LIMITED RETURN FLOW NEAR THE SFC LEADING TO LIMITED COVERAGE OF
SHOWERS AND MAYBE A FEW EMBEDDED THUNDERSTORMS AHEAD AND ALONG A
STRONG SURFACE COLD FRONT APPROACHING FROM THE WEST. WITH THIS...THE
BEST CHANCE FOR MEASURABLE RAIN WILL BE OVER WESTERN AND COASTAL
SECTIONS OF THE FORECAST AREA BY LATE SAT AFTERNOON WITH THE HEAVIER
SHOWERS ALONG WITH A FEW ISOLATED THUNDERSTORMS CONFINED TO THE
COAST OR GENERALLY ALONG AND SOUTH OF THE I-10 CORRIDOR. ALTHOUGH WE
WILL LIKELY SEE SOME DECENT SHEAR AND MID LEVEL FORCING WITH THIS
PATTERN BY SAT AFTERNOON THE THREAT FOR SEVERE WEATHER WILL REMAIN
LOW TO NIL DUE MOSTLY TO VERY LIMITED INSTABILITY. THIS SYSTEM ALSO
LOOKS TO BE RATHER PROGRESSIVE WITH ITS MOVEMENT DUE TO THE LARGE
COLD AIRMASS I AND MUCH THICKNESS VALUES IN ITS WAKE. LATEST MODEL
SOUNDINGS SUPPORT THIS REASONING SHOWING THE BEST MOISTURE PROFILES
OVER THE LOWER PART OF THE FORECAST AREA STRETCHING WELL OFFSHORE BY
SAT AFTERNOON. FOR LATE TONIGHT AND EARLY SAT MORNING LOWER CLOUDS
BEGIN TO DEVELOP ACROSS MOST AREAS WITH MAYBE SOME PATCHY FOG
THROUGH ABOUT 14Z.

AS FOR TEMPS WILL LEAN TOWARDS THE COOLER MAV GUIDANCE FOR LOWS
TONIGHT AND USE A BLEND OF THE MAV/MET MOS GUIDANCE FOR HIGHS ON
SAT. LOWS TONIGHT WILL RANGE FROM THE MID TO UPPER 40S FOR MOST
INLAND AREAS AND THE LOWER TO UPPER 50S CLOSER TO THE COAST. HIGHS
SAT WILL BE IN THE UPPER 60S TO THE NORTH AND THE LOWER 70S CLOSER
TO THE COAST. 32/EE

SHORT TERM /SATURDAY NIGHT THROUGH MONDAY NIGHT/...

POTENTIAL WEATHER IMPACTS THROUGH MONDAY INCLUDE THE POSSIBILITY OF
FREEZING TEMPERATURES SUNDAY NIGHT/MONDAY MORNING.

THE COLD FRONT CONTINUES TO HEAD EAST ACROSS THE FORECAST AREA
SATURDAY NIGHT...AND IS EXPECTED TO REACH CENTRAL FLORIDA SUNDAY
MORNING.  STRONG LOW-LEVEL COLD AIR ADVECTION IS EXPECTED TO SPREAD
SOUTH/EASTWARD ACROSS THE FORECAST AREA SATURDAY EVENING IN WAKE OF
THE FRONT...AS NORTHERLY WINDS PICK UP A BIT IN SPEED.  ISOLATED TO
SCATTERED SHOWERS WILL CONTINUE SOUTH/EAST OF IH-65 SATURDAY
EVENING...AS THE AXIS OF A POWERFUL UPPER-LEVEL TROUGH COMBINES WITH
ANY MOISTURE POOLING NEAR THE FRONT.  PRECIPITATION SHOULD DIMINISH
FROM THE NORTH/WEST AS SATURDAY NIGHT CONTINUES...AS DRIER AIR WORKS
ITS WAY INTO THE REGION.

LINGERING CLOUD COVER SATURDAY NIGHT SHOULD COMBINE WITH ELEVATED
WIND SPEEDS TO TO OFFSET SOME OF THE LOW-LEVEL COLD ADVECTION.  AS
SUCH...FREEZING TEMPERATURES ARE NOT EXPECTED THROUGH SUNDAY
MORNING.  WIND CHILLS...HOWEVER...WILL LIKELY DROP TO 32 (OR
SLIGHTLY BELOW) LATE SATURDAY NIGHT/EARLY SUNDAY MORNING NORTH/WEST
OF IH-65.

ANOTHER REINFORCING SHOT OF COLDER AND DRIER AIR WILL DIVE INTO THE
REGION SUNDAY AS THE UPPER TROUGH FINALLY MOVES EAST OF THE FORECAST
AREA.  THIS WILL ALLOW THE PRESSURE GRADIENT TO WEAKEN...AS A RIDGE
OF SURFACE HIGH PRESSURE STRETCHES FROM THE MID-SOUTH TO CENTRAL
TEXAS.  AS SUCH...HIGH TEMPERATURES SUNDAY WILL LIKELY STRUGGLE TO
MAKE IT INTO THE 50S IN SOME PARTS OF THE CENTRAL GULF
COAST...ESPECIALLY ACROSS SOUTHEAST MISSISSIPPI INTO PARTS OF
CENTRAL ALABAMA.

WITH NEARLY CLEAR SKIES AND LIGHTER WIND SPEEDS...NEARLY IDEAL
CONDITIONS FOR RADIATIONAL COOLING APPEAR TO BE SETTING UP FOR
MONDAY NIGHT/TUESDAY MORNING.  GIVEN THE STRENGTH OF THIS COLD
AIRMASS...CONFIDENCE IS INCREASING THAT OUR AREA WILL LIKELY SEE THE
FIRST WIDESPREAD FREEZE OF THE COLD SEASON AT THIS TIME.
PROBABILISTIC INFORMATION FROM NCEP'S GLOBAL ENSEMBLE SYSTEM
SUGGESTS A "NEAR CERTAINTY" OF AT LEAST FREEZING TEMPERATURES OVER
MOST PLACES (GENERALLY) ALONG AND NORTH OF IH-10.  A FREEZE WATCH
WILL LIKELY BE UNDER CONSIDERATION BY SUBSEQUENT SHIFTS FOR PARTS OF
THE AREA.  AVAILABLE GUIDANCE BLENDS HAVE BEEN UNDERCUT BY SEVERAL
DEGREES TO MORE ADEQUATELY REPRESENT EXPECTED FORECAST CONDITIONS.
/02/

LONG TERM /TUESDAY THROUGH FRIDAY/...

POTENTIAL WEATHER IMPACTS THROUGH FRIDAY INCLUDE THE POSSIBILITY OF
FREEZING TEMPERATURES MONDAY NIGHT/TUESDAY MORNING.

UPPER-LEVEL FLOW BECOMES NEARLY ZONAL HEADING INTO TUESDAY...
RESULTING IN THE SURFACE HIGH PARKING ITSELF ACROSS THE TENNESSEE
VALLEY.  ANOTHER RADIATIONAL COOLING NIGHT MAY BE SEEN AGAIN MONDAY
NIGHT/TUESDAY MORNING...WITH TEMPERATURES AGAIN REACHING FREEZING
(OR A COUPLE OF DEGREES COLDER) OVER PARTS OF THE REGION.  AGAIN...
I HAVE UNDERCUT AVAILABLE GUIDANCE BLENDS BY A COUPLE OF DEGREES TO
MORE ADEQUATELY REPRESENT THE NATURE OF THIS SHALLOW COLD AIRMASS.

NEXT STORM SYSTEM MOVES ONSHORE IN THE PACIFIC NORTHWEST TUESDAY
NIGHT.  AS THE TROUGH DEEPENS TO OUR WEST...EXPECT SHORTWAVE RIDGING
TO DEVELOP ACROSS THE SOUTHEAST IN RESPONSE AS THE FLOW AMPLIFIES IN
THE UPPER ATMOSPHERE.  THIS...COMBINED WITH THE SURFACE HIGH SLIDING
EAST...SHOULD RESULT IN WARMING TEMPERATURES BY THANKSGIVING DAY.
GIVEN THE UNCERTAINTY EVIDENT IN THE ENSEMBLES MEMBERS DURING THIS
TIME PERIOD...I'VE PLAYED IT CONSERVATIVELY FOR NOW.  HOWEVER...
THESE TEMPERATURES MIGHT (AND I EMPHASIZE MIGHT) BE A SKOSH WARMER
DEPENDING ON HOW THINGS EVOLVE.

PEEKING INTO THE CRYSTAL BALL...WE MAY SEE THE NEXT COLD FRONT MOVE
ACROSS OUR AREA SOMETIME NEXT WEEKEND.  TIMING DETAILS ARE PRETTY
SKETCHY AT THIS POINT THOUGH.

THANKS TO THE WFOS IN JACKSON MS AND BIRMINGHAM AL FOR ALL OF THE
COLLABORATIVE EFFORTS THIS AFTERNOON. /02/

MARINE...

HIGH PRESSURE WILL CONTINUE TO BUILD OVER THE NORTH CENTRAL GULF
THROUGH EARLY NEXT WEEK. THIS PATTERN WILL LEAD TO A REINFORCING
COLD FRONT MOVING ACROSS THE MARINE AREA LATE SATURDAY AND SATURDAY
NIGHT. SCATTERED TO NUMEROUS SHOWERS ALONG WITH A FEW THUNDERSTORMS
CAN BE EXPECTED AHEAD OF THE FRONT ESPECIALLY WELL OFFSHORE. A
STRONG OFFSHORE FLOW IS EXPECTED IN THE WAKE OF THE FRONT LATE
SATURDAY NIGHT THROUGH MONDAY MORNING WITH SEAS BUILDING TO NEAR 8
FT WELL OFFSHORE BY LATE SAT NIGHT. AS A RESULT SMALL CRAFT
ADVISORIES WILL LIKELY BE REQUIRED LATE SATURDAY THROUGH EARLY NEXT
WEEK. 32/EE

&&

.MOB WATCHES/WARNINGS/ADVISORIES...
AL...NONE.
FL...NONE.
MS...NONE.
GM...NONE.
&&

THIS PRODUCT IS ALSO AVAILABLE ON THE WEB AT:
HTTP://WEATHER.GOV/MOB

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