FXUS64 KSJT 030550
AFDSJT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN ANGELO TX
1150 PM CST WED DEC 2 2009
.DISCUSSION...
SEE 06Z AVIATION DISCUSSION BELOW.
&&
.AVIATION...
VFR CONDITIONS ARE EXPECTED TO CONTINUE OVER THE NEXT 24
HOUR. LOW LEVEL WINDS WILL REMAIN LIGHT AND VARIABLE OVERNIGHT
BEFORE BECOMING NORTH NORTHEAST AT 10 KNOTS OR LESS LATE
MORNING/EARLY AFTERNOON.
&&
.PREV DISCUSSION... /ISSUED 914 PM CST WED DEC 2 2009/
UPDATE...
UPDATE FOR CURRENT CONDITIONS.
DISCUSSION...
FORECAST FOR TONIGHT IN GOOD SHAPE...AND CHANGES WILL BE FEW.
SKIES HAVE CLEARED ACROSS THE NORTHERN HALF OF WEST CENTRAL
TEXAS...AND WILL UPDATE TO REFLECT THIS IN THE GRIDS AND THE
FORECASTS. ALREADY UNDERCUTTING GUIDANCE NUMBERS ANYWAY...SO DONT
THINK TEMPERATURES WILL NEED TO BE DROPPED. REST OF FORECAST
UNTOUCHED FOR NOW.
PREV DISCUSSION... /ISSUED 516 PM CST WED DEC 2 2009/
DISCUSSION...
SEE 00Z AVIATION DISCUSSION BELOW.
AVIATION...
CURRENT OBS SHOW MVFR CIGS AT ALL TERMINALS...HOWEVER LATEST
SATELLITE SHOWS SOME CLEARING TAKING PLACE ACROSS THE BIG
COUNTRY...SO EXPECT VFR CONDITIONS AT KABI WITHIN THE HOUR AND
THEN EXPECT VFR CONDITIONS AT THE REMAINING TERMINALS BY 02Z. A
HIGH CLOUD DECK WILL BEGIN TO MOVE IN TOMORROW AHEAD OF THE NEXT
SYSTEM. LOW LEVEL WINDS WILL REMAIN NORTHERLY AT 6KT OR LESS
DURING THE OVERNIGHT AND THEN BECOME MORE NORTH NORTHEAST BY
MID MORNING AT 10 KNOTS OR LESS.
PREV DISCUSSION... /ISSUED 410 PM CST WED DEC 2 2009/
SHORT TERM...
COLD SFC RIDGE BUILDING IN FROM THE NORTH LATE THIS AFTERNOON
WHICH WILL BRING DRIER AND COLDER CONDITIONS TO THE REGION
OVERNIGHT. PERSISTENT LOW CLOUDS HOLDING IN ACROSS MUCH OF
THE AREA BUT VISIBLE SAT IMAGERY INDICATING SOME CLEARING ACROSS
FAR NORTHERN PORTIONS OF THE BIG COUNTRY. SHOULD SEE PARTLY CLOUDY
SKIES LATER TONIGHT BUT SOUTHERN ZONES SHOULD SEE MOSTLY
CLOUDY SKIES UNTIL AFTER MIDNIGHT. EXTENT OF CLOUD COVER WILL
MAKE TEMP FORECAST A BIT TRICKY OVERNIGHT BUT SHOULD SEE COLDEST
READINGS OVER CENTRAL AND NORTHERN ZONES WHERE LESS CLOUD COVER
IS EXPECTED. LIGHT NORTH WINDS LESS THAN 10 KT WILL KEEP BOUNDARY
LAYER FROM DECOUPLING BUT LOW LEVEL COLD AIR ADVECTION AND DEWPOINTS
FALLING INTO THE LOW/MID 20S SHOULD ALLOW TEMPS TO FALL INTO THE MID
AND UPPER 20S ACROSS CENTRAL AND NORTHERN SECTIONS WITH UPPER 20S
OVER THE SOUTH.
24
LONG TERM...
THE MAIN CONCERN IS WITH THE PROSPECTS FOR A SNOW EVENT FRIDAY...
FOLLOWED BY THE COLDEST TEMPERATURES SO FAR THIS SEASON FOR LOWS
FRIDAY NIGHT.
THE CLEARING WHICH OCCURS TONIGHT WILL BE SHORT-LIVED...AS
MID-UPPER LEVEL CLOUDS WILL BEGIN TO INCREASE FROM THE NORTH ON
THURSDAY AFTERNOON. MODELS ARE IN GOOD AGREEMENT WITH THE EVOLVING
PATTERN...WITH UPPER TROUGH DEEPENING INTO THE PLAINS AND MIDWEST
THURSDAY INTO FRIDAY. UPPER LEVEL JET ENERGY WILL HELP TO
FACILITATE A DISTURBANCE ROTATING AROUND THE BASE OF THE TROUGH
ACROSS WEST AND CENTRAL TEXAS ON FRIDAY.
TEMPERATURES THURSDAY A CHALLENGE...AS LOW-LEVEL COLD AIR
ADVECTION CONTINUES DESPITE SOME SUNSHINE. GOING WITH HIGHS
40-45 ACROSS MUCH OF WEST CENTRAL TEXAS.
INDICATIONS FAVOR A SNOW EVENT ACROSS WEST CENTRAL TEXAS ON
FRIDAY. MODELS INDICATE FAIRLY STRONG FORCING FOR LIFT...AND A
WINDOW OF AROUND 6 HOURS WHEN THE FORCING IS COINCIDENT WITH
A SATURATED COLUMN IN THE SOUNDINGS. WITH COLD AIR DEEPENING
THROUGHOUT THE COLUMN...SETUP INDICATES ALL SNOW FOR WEST
CENTRAL TEXAS. IN ADDITION...A BRIEF LOOK AT FRONTOGENETIC
FIELDS INDICATE A POTENTIAL FOR BANDS OF OF HEAVIER SNOWFALL.
AT THIS TIME...LEANING TOWARD A SCENARIO OF 1-2 INCHES ACROSS
A FAIRLY LARGE PORTION OF WEST CENTRAL TEXAS...WITH THE LOWER
AMOUNTS IN HASKELL/THROCKMORTON COUNTIES AND CROCKETT COUNTY.
COULD HAVE SCATTERED PATCHES OR AREAS WITH AMOUNTS GREATER
THAN 2 INCHES. LATER SHIFTS WILL BE FURTHER EXAMINING THIS.
THE PRECIPITATION (SNOW) WINDOW LOOKS TO BEGIN AN HOUR OR TWO
BEFORE DAYBREAK ACROSS OUR WESTERN COUNTIES...WITH PRECIPITATION
QUICKLY DEVELOPING INTO OUR EASTERN COUNTIES AROUND MID-MORNING.
WITH THE PROGRESSIVE SYSTEM...SNOW SHOULD BE TAPERING OFF DURING
THE AFTERNOON FROM WEST TO EAST ACROSS OUR AREA.
WITH 850 MB TEMPERATURES OF -6 TO -8 DEGREES C ALONG WITH
EXTENSIVE CLOUD COVER AND PRECIPITATION...BELIEVE TEMPERATURES
ON FRIDAY WILL STRUGGLE TO GET PAST THE FREEZING MARK.
WITH THIS AND THE SNOWFALL AMOUNT CONSIDERATIONS...APPEARS THIS
UPCOMING EVENT WILL BE MORE PROBLEMATIC WITH ROAD CONDITIONS...
AND WE ARE ISSUING A SPECIAL WEATHER STATEMENT TO ADDRESS THE
EXPECTED SCENARIO.
AFTER THIS SYSTEM DEPARTS...COLD SURFACE HIGH WILL DROP SOUTH
ACROSS WEST CENTRAL TEXAS. WITH RADIATIONAL COOLING AND AN
EXPECTATION OF A LIGHT SNOW COVER...APPEARS THAT MUCH OF OUR
AREA COULD HAVE LOWS IN THE UPPER TEENS FRIDAY NIGHT.
A GOOD WARMING TREND IS IN STORE FOR THE WEEKEND WITH DRY
WEATHER...AS SOUTH WINDS DEBVELOP ON SATURDAY AND CONTINUE INTO
SUNDAY.
PATTERN FOR DRY FOR WEST CENTRAL TEXAS EARLY NEXT WEEK WITH A
COUPLE OF COLD FRONTAL PASSAGES.
19
&&
.PRELIMINARY POINT TEMPS/POPS...
ABILENE 44 25 40 25 33 / 20 0 0 30 60
SAN ANGELO 46 26 42 27 33 / 10 0 0 30 70
JUNCTION 48 30 45 31 33 / 10 0 0 20 70
&&
.SJT WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
99/99/28
