Severe Thunderstorm Warning 5, NWS Jackson, MS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON MS
345 AM CST FRI JAN 19 2001

LATEST SURFACE ANALYSIS INDICATES AN ELONGATED AREA OF LOW PRESSURE
AND FRONTAL BOUNDARY STRETCHING FROM SOUTHEAST LOUISIANA TO MIDDLE
TENNESSEE. TWO LOW CENTERS ARE DEFINED...ONE OVER MIDDLE TENNESSEE AND
ONE COMING ONSHORE SOUTHEAST LOUISIANA FROM THE GULF OF MEXICO. A
LARGE AREA OF RAIN...WITH A FEW THUNDERSTORMS...PRETTY MUCH BISECTS
THE CWFA INTO NW AND SE SECTIONS. WARM SECTOR HAS SHIFTED SOMEWHAT
SOUTHEAST TONIGHT...AND LOOKS TO BE FROM NEAR MERIDIAN TO
HATTIESBURG. DEWPOINTS BEHIND BOUNDARY ARE IN THE 30S AND IN THE
WARM SECTOR DEWPOINTS ARE STILL IN THE LOWER TO MID 50S.

MODELS ARE IN GOOD AGREEMENT THIS RUN WITH MASS FIELDS. IN THE UPPER
LEVELS...500MB TROUGH LOOKS TO SWING THROUGH OVERNIGHT/EARLY
SATURDAY AND BE EAST OF THE AREA BY LATE SATURDAY. THERE ARE TWO
MAIN SHORTWAVES ASSOCIATED WITH THIS SYSTEM...ONE FROM THE SOUTHERN
STREAM AND ONE FROM THE NORTHERN STREAM. THE SOUTHERN STREAM
SHORTWAVE WILL MAKE ITS WAY EAST THROUGH THE STATE DURING THE DAY
TODAY. THE NORTHERN STREAM SHORTWAVE WILL MOVE THROUGH THE STATE
OVERNIGHT INTO THE DAY SATURDAY.

THERE WILL BE TWO (POSSIBLY THREE) MAJOR CONCERNS THIS FORECAST
PACKAGE. THE FIRST WILL BE FLOODING. MOST AREAS HAVE SEEN STEADY
RAIN FOR THE PAST 24 HOURS AND THE GROUND IS SATURATED...WITH THE
EXCEPTION OF THE SOUTHEAST. WILL RE-ISSUE A FLOOD WATCH (THROUGH
TODAY) FOR ALL AREAS EXCEPT SOUTHEAST ZONES...WITH MOST AREAS SEEING
AN ADDITIONAL ONE TO THREE INCHES OF RAINFALL. PRECIP AXIS WILL
SHIFT SLOWLY EASTWARD TODAY AS THE SURFACE SYSTEM MOVES OFF TO THE
NORTHEAST/EAST AHEAD OF THE APPROACHING UPPER LEVEL SYSTEM.

THE SECOND CONCERN WILL BE WINTER PRECIPITATION LATE
TODAY/OVERNIGHT.  ETA AND AVN ARE BOTH IN GOOD AGREEMENT WITH THE
ARRIVAL OF THE COLD TEMPERATURES BEHIND THIS FRONTAL SYSTEM. TEMPS
WILL DROP THROUGH THE THIRTIES TODAY...BUT FREEZING AND BELOW
TEMPERATURES ARE NOT EXPECTED TO ARRIVE UNTIL LATER THIS AFTERNOON
IN THE NORTHWEST AND EARLY EVENING FOR POINTS SOUTHEAST. MOISTURE
(ABOVE 850MB) WILL BE ON THE DECREASE OVERNIGHT...BUT GOOD LOW LEVEL
MOISTURE WILL BE AROUND THROUGH THE DAY ON SATURDAY. WITH THE
NORTHERN STREAM SHORTWAVE MOVING THROUGH TONIGHT...WILL NOT RULE OUT
THE POSSIBILITY OF PRECIP. AGREE WITH THE ONGOING PRECIP CHANCES
OVERNIGHT. SNOW AND RAIN/SNOW MIX WILL BE POSSIBLE OVERNIGHT FOR ALL
ZONES EXCEPT SOUTHEAST.

THE THIRD PROBLEM COULD BE FOG...ESPECIALLY IN THE SOUTHEAST ZONES.
THIS AREA HAS SEEN RAIN TODAY AND IS STILL SOMEWHAT IN THE WARM
SECTOR. FOG IS A POSSIBILITY (BEFORE RAIN MOVES IN AGAIN) AND WILL
MONITOR THIS AREA IN CASE VISIBILITIES START DECREASING.

IN THE EXTENDED: CURRENT LOOKS FINE. WEATHER SHOULD BE FAIRLY BENIGN
AND ONLY WITH SLIGHT CHANCES OF PRECIP IN DAY 6/7. TEMPS WILL BE
SOMEWHAT COOLER...WITH HIGHS MAINLY IN THE 40S AND LOWS IN THE 20S
AND 30S.

QPF DISCUSSION: NCEP GUIDANCE LOOKS GUIDANCE LOOKS GOOD. (SEE ABOVE
FOR MORE DETAILED DISCUSSION)

PRELIM NUMBERS...
JAN 40/26/36/20 +2--
MEI 46/29/38/20 +3--

.JA.N...
MS...FLOOD WATCH 018-019-025?055-059>062 TODAY
LA...FLOOD WATCH ALL ZONES TODAY.
AR...FLOOD WATCH ALL ZONES TODAY.

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