Prognostic Meteorological Discussion
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000
FXUS02 KWBC 201742
PMDEPD

EXTENDED FORECAST DISCUSSION...AMENDED
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1241 PM EST MON FEB 20 2017

VALID 12Z THU FEB 23 2017 - 12Z MON FEB 27 2017

OVERVIEW
~~~~~~~~
A STRENGTHENING REX BLOCK ACROSS THE EASTERN PACIFIC CONTINUES TO
BE A PROMINENT FEATURE THROUGH THE PERIOD, SUPPORTING A
STRENGTHENING DOWNSTREAM MEAN TROUGH FROM NUNAVUT INTO THE WEST,
AND RIDGING NEAR THE SOUTHEAST COAST.  THIS PATTERN SHOULD PROMOTE
BELOW NORMAL TEMPS OVER THE WEST AND AT TIMES EXTENDING INTO PARTS
OF THE PLAINS ALONG WITH ABOVE NORMAL TEMPS OVER THE EAST.


MODEL EVALUATION/PREFERENCES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~
OUTSIDE OF THE 00Z UKMET BEYOND THURSDAY MORNING, THE
DETERMINISTIC AND ENSEMBLE GUIDANCE SHOW VERY GOOD AGREEMENT.  AS
SUCH, THE 500 HPA HEIGHTS/PRESSURES/WINDS WERE BASED ON A 00Z
UKMET/00Z ECMWF/00Z CANADIAN/06Z GFS COMPROMISE THURSDAY MORNING
BEFORE SWITCHING TO AN ECMWF/CANADIAN/GFS BLEND FOR LATE THURSDAY,
FRIDAY, AND SATURDAY BEFORE USING INCREASING AMOUNTS OF THE 00Z
NAEFS AND 00Z ECMWF ENSEMBLE MEANS FROM SATURDAY ONWARD.  THE
TEMPERATURES, PRECIPITATION CHANCES, CLOUDS, WEATHER, AND DEW
POINT GRIDS WERE MORE RELIANT ON ENSEMBLE MEANS, AS USUAL.  AN
EARLY DRAFT OF THE DAYS 4-7 QPF WAS BASED ON A ROUGH BLEND OF THE
00Z ECMWF, 06Z GFS, AND 12Z GFS.  THE 12Z GFS WAS MORE USEFUL
EARLY ON, BEFORE ITS MASS FIELDS BECAME OUT OF SYNCH SUNDAY INTO
NEXT MONDAY.


WEATHER HIGHLIGHTS/THREATS
~~~~~~~~~~~~~~~~~~~~~~~~~~
EXPECT THE STORM SYSTEM TRACKING OUT OF THE ROCKIES/PLAINS
THURSDAY TO PASS NEAR CHICAGO TO GENERATE MANY SIGNIFICANT WEATHER
TYPES INCLUDING STRONG WIND, A BAND OF POTENTIALLY HEAVY SNOW IN
THE COMMA HEAD, AND LOCALLY HEAVY RAIN PLUS PSBLY STRONG TO SEVERE
CONVECTION IN THE WARM SECTOR NEAR AND EAST OF THE MS RIVER.
CHECK THE LATEST SPC PRODUCTS FOR UPDATED DETAILS ON THE SEVERE
WEATHER THREAT NEAR INDIANA.  COLD SECTOR TEMPS DO NOT LOOK
PARTICULARLY LOW SO SNOWFALL WOULD OCCUR AT TEMPERATURES CLOSE TO
FREEZING.  LIGHT TO MODERATE SNOW AND COASTAL/LOW ELEVATION RAINS
ARE EXPECTED WITH THE WESTERN TROUGH.  THE NORTHERN PART OF THE
PRECIPITATION SHIELD WITH THE SECOND SYSTEM SUNDAY INTO NEXT
MONDAY COULD CONTAIN SOME WINTRY WEATHER.

UNSEASONABLY WARM TEMPERATURES OVER MUCH OF THE EAST WILL EXTEND
THROUGH LATE WEEK WITH A SIZABLE AREA OF 15-30F+ ANOMALIES AND
POTENTIAL FOR A SLATE OF DAILY RECORD HIGHS AND WARM MINIMA.
WHILE THE COLD FRONT TRAILING FROM THE PLAINS-GREAT LAKES STORM
WILL BRING A SIGNIFICANT COOLING TREND, TEMPERATURES ARE LIKELY TO
REMAIN NEAR TO ABOVE NORMAL WITH AN UPWARD TREND COMMENCING BY
SUNDAY AND NEXT MONDAY.  TEMPERATURES OVER THE WEST SHOULD BE
PERSISTENTLY ON THE COOL SIDE WITH SOME LOCATIONS 10-15F BELOW
NORMAL FOR HIGHS ON ONE OR MORE DAYS.  THIS COOL AIR WILL EXTEND
INTO PARTS OF THE NORTHERN AND CENTRAL PLAINS FROM TIME TO TIME.

ROTH/RAUSCH

$$





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