Friday, January 18, 2008

AREA FORECAST DISCUSSION

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HUNTSVILLE AL
320 AM CST FRI JAN 18 2008

.SHORT TERM...THROUGH SUNDAY...
WEAK COLD FRONT IS CURRENTLY PASSING THROUGH THE HUN CWFA...AND AS
OF 09Z IS IN THE VICINITY OF HSV. THIS IS HELPING TO DISSIPATE THE
STRATUS THAT HAS PERSISTED FOR MUCH OF THE LAST SEVERAL DAYS. SWLY
FLOW PERSISTS ALOFT AHEAD OF A DEEPENING TROUGH IN THE LEE OF THE
ROCKIES...WHICH WILL BE A MAJOR PLAYER ON AREA WX TONIGHT/TMRW.

SHORT-TERM FCST CONTINUES TO BE FOCUSED ON POTENTIAL SNOW EVENT
TONIGHT AND SATURDAY. THE BOTTOM LINE IS THAT OVERALL SNOW POTENTIAL
HAS DECREASED DRAMATICALLY ACROSS MUCH OF THE HUN CWFA...WITH THE
HIGHEST PROBABILITIES EXISTING S/E OF A CULLMAN-SCOTTSBORO LINE.

IN TERMS OF THE SYNOPTIC PATTERN...IN RESPONSE TO THE DEEPENING
TROUGH...CYCLOGENESIS WILL OCCUR ALONG THE THE SRN TX COAST...AND
THE SFC LOW WILL TRACK NEWD INTO THE NCNTRL GULF TONIGHT THEN ON TO
THE CAROLINA COAST SAT NIGHT. MEANWHILE EARLY SAT...AN ARCTIC FRONT
WILL BE SWEEPING INTO NRN AL. THIS GENERAL SETUP HAS NOT SHIFTED
SIGNIFICANTLY FROM PRIOR MDL RUNS. WHAT HAS CHANGED IS THE TIMING...
WHICH HAS SHIFTED 3-6HR LATER...AND A SLIGHT SWD SHIFT IN THE UPPER
JET. SINCE IT WILL BE DIFFICULT FOR THE MOISTURE TO PENETRATE BEHIND
THE ARCTIC FRONT...THE AXIS OF HIGHEST QPF FROM MDL CONSENSUS HAS
SHIFTED WELL TO THE SOUTH AND IS FOCUSED ALONG/SOUTH OF THE I-59
CORRIDOR. 00Z AND 06Z RUNS NOW SHOW THE HUN CWFA ON THE NRN FRINGES
OF THE PCPN...AND THERE IS A POSSIBILITY THAT NWRN AL/SWRN MID TN
MAY SEE LITTLE TO NO PRECIP WHATSOEVER IF CURRENT MODELS VERIFY.

FOR THE FIRST TIME IN RECENT MEMORY CONFIDENCE IN P-TYPE IS HIGH...
WITH LITTLE DOUBT THAT ALMOST EVERYTHING WILL FALL AS SNOW. THE
PROBLEM IS QPF. WHILE THERE WERE TWO VERY DIFFERENT MODEL CAMPS THIS
TIME YESTERDAY...THEY HAVE CONVERGED SHARPLY ON THE MORE SOUTHERLY
SOLN...WITH MINOR VARIATIONS IN THE NRN EXTENT OF THE LIGHTER
PRECIP. HOWEVER...OUR FCST WILL ALLOW FOR THE POSSIBILITY OF A
SLOWER FRONT...OR MORE LIKELY...SLIGHTLY EARLIER PCPN ONSET. THUS
WILL TAPER POPS UP AFTER 06Z TONIGHT...WITH THE HIGHEST CHANCES BTWN
12-18Z TMRW...STILL ONLY TOPPING OUT AT 60 PCT IN OUR SERN AREAS. IN
TERMS OF SNOW AMOUNTS...USING SNOW-WATER RATIOS LESS THAN 10:1 /MORE
REALISTIC FOR THIS AREA/ YIELDS STORM TOTALS LESS THAN 1 INCH FOR
MOST OF THE AREA...BUT APPROACHING 2 INCHES IN SERN LOCATIONS.
WINTER STORM WATCH CRITERIA IS 2 INCHES IN 12 HRS. WITH SOLNS
CONVERGING ON A MORE SOUTHERLY AXIS...CONFIDENCE IN EVEN THIS MORE
LIBERAL APPROACH IS SIMPLY NOT THERE FOR A WATCH...AND FEEL IT IS
TOO EARLY FOR AN ADVISORY. THUS WILL CONTINUE WITH AN SPS...ALBEIT
ONE TONED DOWN FROM THE WETTER SOLNS YESTERDAY.

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