Long Term Discussion

By: NWS
By: NWS

LONG TERM (THURSDAY THROUGH SUNDAY)...
THE LARGE SCALE LONGWAVE PATTERN ALOFT COMMENCES IN NRN STREAM
WITH RIDGE OVER WRN STATES...TROUGHING OVER GREAT LAKES
REGION...WEAK RIDGE OVER ERN STATES AND A TROUGH ACROSS EXTREME
WRN ATLC. SRN STREAM MARKED BY FLAT RIDGE FROM BAJA CA EWD INTO
WRN ATLC. LARGE MID TO UPPER LEVEL HIGH REMAINS OVER THE GULF
WATERS KEEPING OUR WEATHER DRY AND PRETTY WARM. AT SURFACE...LOW
OVER SRN GREAT LAKES REGION WITH STATIONARY FRONT E THEN SE ACROSS
N GA...AND A COLD FRONT SWWD INTO OK. SOUTH OF STATIONARY
FRONT...RIDGING FROM WRN ATLC WSW ACROSS NE GULF. THUS DEEP LAYER
HIGH PRESSURE CONTROLS NE GULF.

SOME DIVERGENCE IN MODELS SEEN BEGINNING ON FRIDAY. GREAT LAKES
TROUGH WILL DIG THROUGH THE TENNESSEE VALLEY FRIDAY INTO SATURDAY.
DRY WEST TO NW FLOW ALOFT WILL HELP PUSH THE WEAKENING COLD FRONT
INTO NRN ALA/GA. MODELS DIVERGE AT THIS POINT WITH ECMWF STALLING
FRONT THERE WHILE GFS BRINGS IT INTO CNTRL AL/GA. IN EITHER CASE...
TROUGH THEN EXITS INTO ATLC WITH DEAMPLIFYING UPPER PATTERN REST OF
EXTENDED HIGHLIGHTED BY PASSING IMPULSES MOVING EWD IN INCREASINGLY
ZONAL FLOW IN NRN STREAM. THIS TRANSLATES TO DECREASING DYNAMICS
WHICH ALLOWS FRONT TO STALL AND THEN WASH OUT. SO...SURFACE HIGH
PRESSURE WILL REMAIN NORTHEAST OF CWA WITH AXIS WSW OVER LOCAL AREA
REMAINDER OF THE WEEKEND. THIS TRANSLATES TO ENE LOW LEVEL FLOW
TRAVERSING LAND SO MOISTURE WILL REMAIN LIMITED WITH LITTLE OR NO
CHANCE FOR RAIN DURING THIS EXTENDED PERIOD.

EVEN MORE MODEL DIVERGENCE DAY BEGINNING SUNDAY. THE ECMWF HAS
A NOTABLY WEAKER UPPER RIDGE THAN GFS AND IF THIS PANS OUT...IT
COULD ALLOW STRONG HURRICANE IGOR TO EDGE CLOSER TO SE COAST WITH
SOME MOISTURE SPREADING WWD INTO CWA BY LATE DAY 7. CONVERSELY..GFS
KEEPS STRONGER RIDGE IN PLACE OVER EAST COAST AND ADJACENT ATLC EVEN
REINFORCING THE DRY AIR OVER GULF REGION FRI-SUN. IN GFS SCENARIO
THUS IGOR TURNS WELL EAST OF COASTLINE. BASED ON PREV RUNS...WILL
LEAN TOWARDS GFS BUT CONFIDENCE NOT EXCEEDINGLY HIGH.

WILL GO WITH NIL POPS THUR SAT NIGHT THEN WDLY SCT POPS SUN-MON.
WITH LOCAL AREA TO REMAIN IN WARM SECTOR BOTH MIN AND MAX TEMPS WILL
REMAIN SEVERAL DEGREES ABOVE CLIMO...67-70 DEGREE LOWS AND 90 TO 93
DEGREE HIGHS.


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