“AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TALLAHASSEE FL
943 PM EST MON MAR 4 2019
NEAR TERM [THROUGH TONIGHT]
COMPLEX FORECAST SCENARIO FOR TONIGHT. OBSERVATIONAL DATA SHOW A
WEAK SHORTWAVE MOVING ACROSS THE SOUTHEAST AND THIS IS CREATING AN
AREA OF MAINLY LIGHT PRECIP THAT EXTENDS FROM COASTAL LOUISIANA
NORTHEASTWARD INTO WEST CENTRAL GEORGIA. AS THIS SHORTWAVE
CONTINUES MOVING EASTWARD THE MAIN FORCING FOR PRECIP WILL SHIFT
LIGHT RAIN OVER MUCH OF OUR AREA OVERNIGHT AND INTO THE EARLY
MORNING HOURS ON TUESDAY.
WHAT PRESENTS SOME DEGREE OF CHALLENGE TO THIS FORECAST IS THAT A
COOLER AIRMASS CONTINUES TO ADVECT INTO THE REGION. WHILE THE VAST
MAJORITY OF OUR FORECAST AREA WILL SEE LOWS GENERALLY IN THE UPPER
30S TO LOWER 40S, THERE IS SOME POTENTIAL FOR SURFACE TEMPERATURES
TO DROP INTO THE LOW TO MID 30S ACROSS OUR FAR NORTHWESTERN
COUNTIES.
A DEEPER EXAMINATION OF THE ATMOSPHERIC PROFILE IN MODEL SOUNDINGS
ACROSS OUR FAR NORTHWESTERN COUNTIES REVEALS PRECIP GENERATING IN
A MAINLY ABOVE FREEZING CLOUD LAYER ACROSS OUR FORECAST AREA IN
THE 03-09Z TIME FRAME. BELOW THE CLOUD BASE, THE TEMPERATURE
PROFILE COOLS DUE TO ADVECTIVE AND EVAPORATIVE EFFECTS AND DROPS
BELOW FREEZING (IN THE COLDEST OF THE MODELS) AROUND 3500 FT AGL.
THE IMMEDIATE NEAR SURFACE LAYER REMAINS JUST ABOVE FREEZING IN
NEARLY ALL MODEL SOLUTIONS. THIS PARTICULAR ATMOSPHERIC PROFILE
IS SUGGESTIVE OF SOME RAIN MIXING WITH ICE PELLETS GIVEN THE DEPTH
OF THE SUB-FREEZING LAYER. THE AREA MOST LIKELY TO SEE ANY TYPE
OF MIX WOULD BE ALONG AND NORTH OF A LINE FROM NEAR ELBA, AL
EASTWARD TO GEORGETOWN, GA. AREAS SOUTH AND WEST OF THIS AREA DO
NOT LOOK TO HAVE A SUFFICIENTLY DEEP COOL SUB-CLOUD LAYER TO
SUPPORT ANY FREEZING OF THE HYDROMETEOR BEFORE REACHING THE
SURFACE. EVEN WITHIN THE COOLER AREA, CONFIDENCE IN THIS
OCCURRING IS FAIRLY LOW - THOUGH THE POSSIBILITY IS NOT ZERO. FOR
NOW, PREFER TO MONITOR CURRENT TRENDS IN OBSERVATIONS AS THE T/TD
SPREADS ACROSS SOUTHEAST ALABAMA ARE FAIRLY LOW, WHICH SUGGESTS
ANY EVAPORATIVE EFFECTS, WHICH WOULD AID IN GREATER COOLING OF THE
ATMOSPHERIC COLUMN, MAY BE MINIMIZED ENOUGH TO PREVENT ANY
OBSERVATION. THUS, HAVE NOT INCLUDED ANY MENTION OF ICE PELLETS
MIXING WITH RAIN IN THIS FORECAST UPDATE. IT SHOULD BE NOTED THAT
WERE ANY MIX OF ICE PELLETS TO OCCUR, WITH SURFACE TEMPERATURES
ABOVE FREEZING, THERE WOULD BE NO ACCUMULATION - THUS NO
ADVISORIES ARE NEEDED.”
NATIONAL WEATHER SERVICE TALLAHASSEE FL
943 PM EST MON MAR 4 2019
NEAR TERM [THROUGH TONIGHT]
COMPLEX FORECAST SCENARIO FOR TONIGHT. OBSERVATIONAL DATA SHOW A
WEAK SHORTWAVE MOVING ACROSS THE SOUTHEAST AND THIS IS CREATING AN
AREA OF MAINLY LIGHT PRECIP THAT EXTENDS FROM COASTAL LOUISIANA
NORTHEASTWARD INTO WEST CENTRAL GEORGIA. AS THIS SHORTWAVE
CONTINUES MOVING EASTWARD THE MAIN FORCING FOR PRECIP WILL SHIFT
LIGHT RAIN OVER MUCH OF OUR AREA OVERNIGHT AND INTO THE EARLY
MORNING HOURS ON TUESDAY.
WHAT PRESENTS SOME DEGREE OF CHALLENGE TO THIS FORECAST IS THAT A
COOLER AIRMASS CONTINUES TO ADVECT INTO THE REGION. WHILE THE VAST
MAJORITY OF OUR FORECAST AREA WILL SEE LOWS GENERALLY IN THE UPPER
30S TO LOWER 40S, THERE IS SOME POTENTIAL FOR SURFACE TEMPERATURES
TO DROP INTO THE LOW TO MID 30S ACROSS OUR FAR NORTHWESTERN
COUNTIES.
A DEEPER EXAMINATION OF THE ATMOSPHERIC PROFILE IN MODEL SOUNDINGS
ACROSS OUR FAR NORTHWESTERN COUNTIES REVEALS PRECIP GENERATING IN
A MAINLY ABOVE FREEZING CLOUD LAYER ACROSS OUR FORECAST AREA IN
THE 03-09Z TIME FRAME. BELOW THE CLOUD BASE, THE TEMPERATURE
PROFILE COOLS DUE TO ADVECTIVE AND EVAPORATIVE EFFECTS AND DROPS
BELOW FREEZING (IN THE COLDEST OF THE MODELS) AROUND 3500 FT AGL.
THE IMMEDIATE NEAR SURFACE LAYER REMAINS JUST ABOVE FREEZING IN
NEARLY ALL MODEL SOLUTIONS. THIS PARTICULAR ATMOSPHERIC PROFILE
IS SUGGESTIVE OF SOME RAIN MIXING WITH ICE PELLETS GIVEN THE DEPTH
OF THE SUB-FREEZING LAYER. THE AREA MOST LIKELY TO SEE ANY TYPE
OF MIX WOULD BE ALONG AND NORTH OF A LINE FROM NEAR ELBA, AL
EASTWARD TO GEORGETOWN, GA. AREAS SOUTH AND WEST OF THIS AREA DO
NOT LOOK TO HAVE A SUFFICIENTLY DEEP COOL SUB-CLOUD LAYER TO
SUPPORT ANY FREEZING OF THE HYDROMETEOR BEFORE REACHING THE
SURFACE. EVEN WITHIN THE COOLER AREA, CONFIDENCE IN THIS
OCCURRING IS FAIRLY LOW - THOUGH THE POSSIBILITY IS NOT ZERO. FOR
NOW, PREFER TO MONITOR CURRENT TRENDS IN OBSERVATIONS AS THE T/TD
SPREADS ACROSS SOUTHEAST ALABAMA ARE FAIRLY LOW, WHICH SUGGESTS
ANY EVAPORATIVE EFFECTS, WHICH WOULD AID IN GREATER COOLING OF THE
ATMOSPHERIC COLUMN, MAY BE MINIMIZED ENOUGH TO PREVENT ANY
OBSERVATION. THUS, HAVE NOT INCLUDED ANY MENTION OF ICE PELLETS
MIXING WITH RAIN IN THIS FORECAST UPDATE. IT SHOULD BE NOTED THAT
WERE ANY MIX OF ICE PELLETS TO OCCUR, WITH SURFACE TEMPERATURES
ABOVE FREEZING, THERE WOULD BE NO ACCUMULATION - THUS NO
ADVISORIES ARE NEEDED.”
