Prognostic Meteorological Discussion
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FXUS02 KWBC 240643
PMDEPD

EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
242 AM EDT FRI MAR 24 2017

VALID 12Z MON MAR 27 2017 - 12Z FRI MAR 31 2017

...OVERVIEW/GUIDANCE EVALUATION/PREFERENCES...

LATEST GUIDANCE MAINTAINS THE THEME OF AN ACTIVE WEATHER PATTERN
FEATURING A SERIES OF ERN PAC SHRTWVS FEEDING INTO AND THEN
EJECTING FROM A WRN U.S. MEAN TROUGH.  A SEPARATE NRN STREAM
ACROSS THE NRN TIER STATES AND SRN CANADA WILL AT TIMES HAVE SOME
INFLUENCE ON SYSTEM TRACK/PROGRESSION WHETHER DIRECTLY OR
INDIRECTLY.

AS A WHOLE THE MODELS/ENSEMBLE MEANS ARE IDENTIFYING EMBEDDED
FEATURES FAIRLY WELL BUT DIFFER IN SOME OF THE DETAILS SUCH AS
AMPLITUDE AND TIMING.  FOR DAYS 3-5 MON-WED AN OPERATIONAL MODEL
BLEND INCLUDING VARIOUS WEIGHTS OF THE 12Z-18Z GFS AND 12Z
ECMWF/UKMET/CMC REPRESENTED CONSENSUS IDEAS WELL WHILE MAINTAINING
AN INTERMEDIATE SOLN WHERE DIFFS EXIST.  THEN DAYS 6-7 THU-FRI
UTILIZED THE 18Z GEFS/12Z ECMWF MEANS ALONG WITH SOME OPERATIONAL
MODEL INPUT.  THE RESULTING FCST KEPT CONTINUITY CHANGES FAIRLY
MODEST.

AS A WEAKENING SYSTEM REACHES THE GRTLKS MON ANOTHER SYSTEM
EMERGING FROM THE PLAINS/MS VLY WILL TRACK NORTHEASTWARD WITH
MODELS/ENSEMBLES UNDECIDED OVER SPECIFICS OF ENERGY ALOFT AND TO
WHAT EXTENT LOW PRESSURE MAY BE DEFLECTED BY INITIAL ERN
CANADA/NEW ENGLAND SFC RIDGE.  RECENT GFS RUNS HAVE TENDED TO BE
ON THE SLOWER SIDE OF THE SPREAD ALOFT BUT THEIR MORE SUPPRESSED
SFC LOW PRES MERITS PARTIAL CONSIDERATION.

NEXT SYSTEM WILL ENTER THE WEST ON MON AND LIKELY CLOSE OFF A LOW
OVER THE SOUTHWEST/SRN ROCKIES BY TUE AND THEN TRAVEL GRADUALLY
EWD THEN NEWD... REACHING INTO THE CNTRL PLAINS OR MS VLY BY FRI.
12Z/18Z GFS RUNS AND SOME GEFS MEMBERS WERE A BIT ON THE SLOWER
SIDE OF THE ENVELOPE FROM FAIRLY EARLY IN THE PERIOD BUT THE 00Z
GFS HAS TRENDED SIGNIFICANTLY FASTER AND 00Z UKMET/CMC RUNS HAVE
ALSO TRENDED FASTER THAN THEIR 12Z COUNTERPARTS.  TOWARD DAYS 6-7
THU-FRI SLOWER TIMING IN THE 12Z AND ESPECIALLY 18Z GFS WAS
PARTIALLY DUE TO GREATER NERN U.S. TROUGH AMPLITUDE THAT HAD AT
BEST MODEST SUPPORT FROM THE ENSEMBLE MEANS.  TIMING OF THIS
SYSTEM WILL LIKELY BE AN ONGOING UNCERTAINTY FOR A WHILE.

THE NEXT SHRTWV OF INTEREST SHOULD APPROACH THE WEST COAST AROUND
LATE WED AND THEN RAPIDLY AMPLIFY OVER THE WEST.  THUS FAR
OPERATIONAL MODEL RUNS SUGGEST DECENT CONFIDENCE IN AN UPR LOW
CLOSING OFF OVER THE SWRN STATES LATE IN THE WEEK... SUPPORTING
PARTIAL INCLUSION OF OPERATIONAL SOLNS TO ENHANCE DEFINITION VS
THE ENSEMBLE MEANS THU-FRI.


...SENSIBLE WEATHER HIGHLIGHTS/THREATS...

THE SUCCESSION OF SYSTEMS DURING THE PERIOD WILL LIKELY SPREAD ONE
OR MORE EPISODES OF MEANINGFUL PRECIP ACROSS A SIGNIFICANT PORTION
OF THE LOWER 48 DURING THE PERIOD.  THE EXTREME SOUTHWEST AND THE
FL PENINSULA HAVE THE BEST CHANCE TO STAY FAIRLY DRY NEXT WEEK.
COMBINATION OF A LEADING SYSTEM AND NEXT ONE TO EMERGE FROM THE
PLAINS/MS VLY WILL SPREAD AREAS OF RAIN OF VARYING INTENSITY
THROUGH MUCH OF THE EAST DURING THE FIRST HALF OF THE WEEK WITH
TEMPS PSBLY COLD ENOUGH FOR WINTRY PRECIP OVER NRN NEW ENGLAND.
POTENTIAL FOR SEVERE CONVECTION EXISTS OVER THE VICINITY OF THE
S-CNTRL MS VLY EARLY IN THE WEEK.  THE SYSTEM ENTERING THE WEST AT
THE START OF THE WEEK WILL SPREAD RAIN AND HIGHER ELEV SNOW ACROSS
MUCH OF THE WEST AT FIRST AND THEN BY MID-LATE WEEK GENERATE AREAS
OF RAIN/CONVECTION FROM THE SRN HALF OF THE HIGH PLAINS EWD/NEWD.
SOME OF THIS ACTIVITY MAY BE HVY TO EXCESSIVE AND STRONG/SEVERE
CONVECTION IS PSBL AS WELL.  CONSULT SPC OUTLOOKS FOR LATEST INFO
REGARDING SEVERE THREATS AS DETAILS GAIN MORE CLARITY.  THE FINAL
SYSTEM OF INTEREST SHOULD BRING MSTR INTO THE PAC NW BY WED WITH
PRECIP SPREADING SEWD ACROSS THE WEST IN FOLLOWING DAYS WHILE SNOW
LVLS DECREASE.

WITH THE ACTIVE PATTERN LEADING TO CONSIDERABLE COVERAGE OF
CLOUDS/PRECIP... EXPECT MUCH OF THE LOWER 48 TO AVERAGE ABOVE
NORMAL FOR MIN TEMPS NEXT WEEK.  THE WEST COAST STATES AND
INTERIOR WEST SHOULD SEE ONE OR MORE DAYS OF BELOW NORMAL HIGHS
WHILE NEW ENGLAND MAY BE ON THE CHILLY SIDE EARLY IN THE WEEK.
THE SOUTH AND PARTS OF THE NRN TIER SHOULD BE MOST CONSISTENTLY
ABOVE NORMAL FOR HIGHS.  STRONG FRONT DRAPED OVER/NEAR THE NRN MID
ATLC DURING THE FIRST HALF OF THE WEEK WILL LEAD TO A DIFFICULT
FCST FOR TEMPS IN ITS VICINITY.

RAUSCH

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