Prognostic Meteorological Discussion
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FXUS02 KWBC 171331
PMDEPD

EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
830 AM EST TUE JAN 17 2017

VALID 12Z FRI JAN 20 2017 - 12Z TUE JAN 24 2017

...MORE WET WEATHER SLATED FOR CA, FURTHER RELIEVING DROUGHT
CONDITIONS...
...HEAVY PRECIPITATION EXPECTED FROM THE SOUTHEAST THROUGH THE
MID-ATLANTIC STATES INTO SOUTHERN NEW ENGLAND...


OVERVIEW & MODEL PREFERENCES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~
ZONAL FLOW ACROSS THE PACIFIC INTO THE LOWER 48 ACTS TO ROLL UP
CLOSED CYCLONES EAST OF THE ROCKIES DURING THE MEDIUM RANGE PERIOD
UNDER THE BASE OF A BURGEONING 500 HPA HEIGHT ANOMALY OVER HUDSON
BAY/QUEBEC.  THE GUIDANCE SHOWS VERY GOOD AGREEMENT THROUGH THE
PERIOD.  AS SUCH, THE PRESSURES, 500 HPA HEIGHTS, WINDS WERE BASED
ON A COMPROMISE OF THE 00Z CANADIAN, 00Z UKMET, 06Z GFS, 00Z ECMWF
EARLY ON BEFORE USING INCREASING AMOUNTS OF THE 00Z NAEFS AND 00Z
ECMWF ENSEMBLE MEAN FROM SUNDAY ONWARD.  THE TEMPERATURES, DEW
POINTS, CLOUDS, WEATHER, AND PRECIPITATION CHANCE GRIDS WILL BE
BASED ON A MORE ENSEMBLE MEAN-HEAVY BLEND, AS USUAL.  THE PLAN FOR
THE DAY 4-7 QPF IS FOR A SOLUTION CLOSE TO A 06Z GFS/00Z ECMWF
COMPROMISE.


WEATHER HIGHLIGHTS/THREATS
~~~~~~~~~~~~~~~~~~~~~~~~~~
CONFIDENCE REMAINS ABOVE AVERAGE FOR AT LEAST A COUPLE EPISODES OF
SIGNIFICANT RAIN/HIGH ELEVATION SNOW AND STRONG WINDS ALONG THE
WEST COAST WITH THIS ENHANCED ACTIVITY EXTENDING INTO THE SIERRA
NEVADA RANGE AND SOUTHWEST.  CONTINUE TO EXPECT AREAL AVERAGE
AMOUNTS TO LIE IN THE 5-8 INCH AMOUNTS ALONG SOME COASTAL
LOCATIONS AND OVER THE SIERRA NEVADA WITH POTENTIALLY HIGHER
TOTALS ALONG WINDWARD SLOPES.  FOR SRN CA/AZ THE HEAVIEST PRECIP
SHOULD OCCUR AROUND FRI-FRI NIGHT AND AGAIN AROUND SUN-MON.  MUCH
OF THE REMAINDER OF THE WEST SHOULD SEE LIGHTER PRECIPITATION.
THE UNSETTLED WEATHER WILL TEND TO KEEP TEMPERATURE RANGES MORE
NARROW THAN USUAL WITH BELOW NORMAL HIGHS... ON A LOCALIZED BASIS
BY GREATER THAN 10F... AND NEAR TO ABOVE NORMAL LOWS.

PORTIONS OF THE EAST/MIDWEST WILL SEE SOME RAIN ON FRI FOLLOWED BY
A BRIEFLY DRIER PERIOD.  LOCALLY MDT/HVY RNFL MAY DEVELOP NEAR THE
GULF COAST AROUND FRI NIGHT-SAT ALONG A LINGERING FRONT.  AS
ENERGY FROM THE INITIAL WEST COAST STORM CROSSES THE
PLAINS/SOUTHEAST... MORE HEAVY RAINS MAY DEVELOP AND SPC IS
MONITORING THE POTENTIAL FOR SEVERE CONVECTION NEAR THE ERN HALF
OF THE GULF COAST DURING THE WEEKEND.  CONSULT LATEST SPC PRODUCTS
FOR FURTHER INFORMATION.  THE PLAINS TO OH VLY/MID ATLC SYSTEM
WILL SPREAD A BROAD AREA OF PCPN MOSTLY IN THE FORM OF RAIN ACROSS
THE ERN HALF OF THE COUNTRY.  THERE IS STILL A FAIRLY GOOD SIGNAL
FOR A PERIOD OF STRONG LOW LEVEL INFLOW FROM THE ATLANTIC THAT
WOULD ENHANCE RAINS ALONG THE EAST COAST/ERN SLOPES OF THE
APLCHNS.  IT STILL APPEARS THAT ANY SNOW THAT DOES OCCUR WOULD BE
LIMITED TO NEAR THE UPPER LOW MOVING ACROSS THE SOUTHERN TIER OF
THE COUNTRY AND TERRAIN OF THE APPALACHIANS AND AT THE NRN FRINGE
OF THE MSTR SHIELD IF IT REACHES CLOSE TO THE CANADIAN BORDER.
WITHIN A PATTERN OF ABOVE TO MUCH ABOVE NORMAL TEMPS OVER MOST
AREAS EAST OF THE ROCKIES... THE UPPER MS VALLEY CONTINUES TO BE
THE EXPECTED FOCUS FOR HIGHEST ANOMALIES... AVERAGING PLUS 25-35F
FOR MINS OVER THE 5-DAY PERIOD.  THERE MAY BE MULTIPLE DAYS WITH
MORNING LOWS NEAR OR ABOVE RECORD WARM VALUES.

ROTH/RAUSCH
$$




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