Prognostic Meteorological Discussion
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000
FXUS02 KWBC 161353
PMDEPD

EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
853 AM EST MON JAN 16 2017

VALID 12Z THU JAN 19 2017 - 12Z MON JAN 23 2017

...HEAVY PRECIPITATION RETURNS TO CALIFORNIA, EXPECTED TO FURTHER
ERODE DROUGHT CONDITIONS...


GUIDANCE EVALUATION/PREFERENCES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
THE EXPECTED PATTERN FEATURES TROUGHING ACROSS THE WEST AND
INCREASED RIDGING ACROSS EASTERN CANADA AS A POSITIVE ANOMALY NEAR
JAMES/HUDSON BAY STRENGTHENS AND INCREASES IN SIZE WITH TIME.
THIS SHOULD INCREASE BLOCKING ACROSS THE EASTERN HALF OF THE
CONTINENT.

SINCE THE GUIDANCE IS IN SUCH GOOD AGREEMENT, THE PRESSURES/500
HPA HEIGHTS/WIND GRIDS ARE BASED ON A COMPROMISE OF THE 00Z
CANADIAN, 00Z UKMET, 06Z GFS, AND 00Z ECMWF THROUGH THURSDAY.
THEREAFTER, SLOWLY INCREASING PERCENTAGES OF THE 00Z NAEFS/00Z
ECMWF ENSEMBLE MEANS WERE USED.  AS USUAL, THE TEMPERATURE, DEW
POINT, CLOUDS, WEATHER, AND PRECIPITATION CHANCE GRIDS ARE MORE
ENSEMBLE MEAN BASED TO TAKE INTO ACCOUNT THE UNCERTAINTY.  THE
DAYS 4-7 QPF IS GOING TO RESEMBLE A COMPROMISE OF THE 00Z ECMWF
AND 06Z GFS, THE WAY THINGS LOOK RIGHT NOW.


WEATHER HIGHLIGHTS/THREATS
~~~~~~~~~~~~~~~~~~~~~~~~~~
A SERIES OF PACIFIC SYSTEMS WILL BRING PERIODS OF HEAVY RAIN AND
HIGH ELEVATION SNOW MAINLY TO CALIFORNIA AND ARIZONA.  AREAL
AVERAGE AMOUNTS IN CA SHOULD BE 5-10", WITH LOCALLY HIGHER AMOUNTS
POSSIBLE ON WINDWARD FACING SLOPES.  THE BEST SURGE OF
MOISTURE/RAIN ACROSS SOUTHERN CA AND INTO FAVORED TERRAIN OF AZ
APPEARS MOST LIKELY FRIDAY AND FRIDAY NIGHT.  MUCH OF THE
REMAINDER OF THE WEST SHOULD SEE LIGHTER RAINS AND INLAND/HIGHER
ELEV SNOW.  THE UNSETTLED WEATHER WILL KEEP HIGHS BELOW NORMAL
MOST AREAS WITH LOW TEMPERATURES NEAR TO ABOVE NORMAL.

ACROSS THE GREAT LAKES, MISSISSIPPI VALLEY, AND EAST, EJECTING
PLAINS/MEXICO ENERGY WILL GENERATE ONE AREA OF POTENTIALLY HVY
RNFL FROM THE W-CNTRL GULF COAST INTO PARTS OF THE SOUTHEAST AND
TN VLY/SRN APLCHNS EARLY IN THE PERIOD.  A LINGERING SURFACE FRONT
ALONG THE GULF COAST COULD FOCUS ADDITIONAL RAINS DURING THE
WEEKEND.  THE LARGE SCALE PLAINS-ERN U.S. SYSTEM SUNDAY INTO
MONDAY WILL BE ACCOMPANIED BY A BROAD PRECIPITATION SHIELD.  WITH
EACH EPISODE THERE MAY BE POTENTIAL FOR SOME CONVECTION TO BE ON
THE STRONG SIDE OVER SOUTHERN AREAS.  THERE MAY BE A PERIOD OF
STRONG ATLANTIC INFLOW THAT COULD ENHANCE RNFL ALONG PORTIONS OF
THE EAST COAST/ERN SLOPES OF THE APPALACHIANS, THOUGH INSTABILITY
SHOULD BE MEAGER AS USUAL FOR THIS TIME OF THE YEAR.  GIVEN THE
GENERAL FLOW PATTERN, THIS STORM MAY GENERATE AN UNUSUALLY SMALL
COVERAGE OF SNOW FOR SUCH A MASSIVE SYSTEM IN THE LATTER HALF OF
JANUARY.  WHAT SNOW THERE IS MAY BE CONFINED TO NEAR THE UPPER LOW
(AS 500 HPA HEIGHTS ARE PROGGED TO BE NEAR/BELOW 5340 METERS) AND
OVER THE NORTHERN PLAINS.  MUCH ABOVE NORMAL TEMPS OVER MOST AREAS
EAST OF THE ROCKIES ARE EXPECTED WITH SOME 30F+ ANOMALIES AND
POSSIBLE DAILY RECORD WARM LOW READINGS CENTERED OVER/NEAR THE
UPPER MS VALLEY.

ROTH/RAUSCH
$$




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