Prognostic Meteorological Discussion
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FXUS02 KWBC 190659
PMDEPD

EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
158 AM EST SUN NOV 19 2017

VALID 12Z WED NOV 22 2017 - 12Z SUN NOV 26 2017

...RECORDS HIGHS LIKELY IN THE SOUTHWEST LATER NEXT WEEK AND WET
OVER THE NWRN US...


...OVERVIEW...

AN AMPLIFIED MEAN FLOW PATTERN WILL BE HIGHLIGHTED BY AN ERN
PACIFIC UPPER TROUGH...A VERY STRONG UPPER HIGH NEAR THE DAVIS
STRAIT...AND A SECONDARY UPPER HIGH NEAR SRN CALIFORNIA WILL
CONTINUE TO FAVOR ERN CONUS TROUGHING ALOFT NEXT WEEK. A LEAD
SYSTEM WILL PUSH OFF THE EAST COAST WEDNESDAY AS PROPELLED BY
AMPLE APPROACHING NRN STREAM TROUGH ENERGY. HOWEVER...THE FRONT
SHOULD LINGER THROUGH THE WEEK OVER WETTENED FLORIDA AS MORE SRN
STREAM ENERGY DIGGING TO THE LEE OF THE WRN US RIDGE OFFERS SOME
FLOW SEPARTION POTENTIAL. MEANWHILE...ANOTHER SYSTEM WILL ENTER
THE PACIFIC NORTHWEST BY THURSDAY/THANKSGIVING AND MOVE EASTWARD
THROUGH THE HIGH PLAINS ON FRIDAY AND ACROSS THE EAST-CENTRAL THEN
ERN US NEXT WEEKEND.


...GUIDANCE/UNCERTAINTY PREFERENCES......

MODELS/ENSEMBLES ARE IN GOOD AGREEMENT ON THE LARGE SCALE
PATTERN...BUT HAVE LINGERING ISSUES WITH THE DETAILS. SURFACE HIGH
AND LOW SYSTEM RESPONSES TO UNCERTAIN AND CHANGING STRENGTH/TIMING
ISSUES OF EMBEDDED IMPULSES ALOFT CONTINUE TO WRECK HAVIC WITH
ASSOCIATED SENSIBLE WEATHER FOCUS AT LOWER LEVELS OF THE
ATMOSPHERE. THIS IS PRODUCING HIGHLY ERRATIC AND MAINLY UNRESOLVED
RUN TO RUN MODEL LOCAL CONSISTENCY ISSUES...ESPECIALLY WITH
RESPECT TO FLOW SEPARATION EXTENT AND PROGRESSION NEAR/OFF THE
GULF COAST AND SERN US/FL. WHILE SOME INPUT FROM MODEL GUIDANCE
CAN BE CONSIDERED...MAINLY FAVOR AN ENSEMBLE MEAN BASED FORECAST
STRATEGY USING REASONABLY COMPATABLE AND CONSISTENT GEFS/ECMWF
ENSEMBLE MEANS.


...WEATHER HIGHLIGHTS...

MORE WET FLOW IS ON TAP FOR THE PACIFIC NW WITH OCCASIONALLY HEAVY
DAILY RAINS AND LOCALLY HEAVY ELEVATION SNOWS. UPPER RIDGING WILL
SUPPORT WELL ABOVE AVERAGE TEMPERATURES IN THE SOUTHWEST WHERE
RECORD HIGHS ARE POSSIBLE WED-SAT OVER PARTS OF CA/NV/AZ/UT. MILD
TEMPERATURES WILL EXTEND EASTWARD THROUGH THE CENTRAL/SOUTHERN
ROCKIES AND PLAINS AHEAD OF A COLD FRONT THU/FRI. COOLER THAN
AVERAGE TEMPERATURES ARE EXPECTED IN THE EASTERN US BEHIND THE
INITIAL COLD FRONT WEDNESDAY. THERE IS A GOOD CHANCE FOR
APPRECIABLE PRECIPITATION ALONG THE GULF COAST AS LOW PRESSURE
CENTERS MEANDER ALONG A SLOW MOVING FRONT. EXPECT SOME RAIN/SNOW
AROUND THE GREAT LAKES BUT GENERALLY NO PRECIPITATION FROM THE
SOUTHWEST TO THE PLAINS AND MS VALLEY.


...THANKSGIVING FORECAST...

IT WILL REMAIN GENERALLY QUIET FOR MOST OF THE LOWER 48.
PRECIPITATION WILL BE MOST CONCENTRATED IN THE PACIFIC NORTHWEST
INTO NORTHERN CALIFORNIA AS WELL AS NORTHERN IDAHO/WESTERN
MONTANA/NW WYOMING. RAIN IS ALSO QUITE POSSIBLE THROUGH FLORIDA
AND THE COASTAL SOUTHEAST DEPENDING ON HOW THE SURFACE SYSTEMS
EVOLVE. RECORD HIGH TEMPS ARE POSSIBLE IN THE SOUTHWEST WITH
WIDESPREAD 80S AND SOME 90S...BUT COOLER 30S/40S IN THE UPPER
MIDWEST/GREAT LAKES/NORTHEAST/MID-ATLANTIC.


SCHICHTEL/FRACASSO


$$





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