Prognostic Meteorological Discussion
Issued by NWS

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2
000
FXUS02 KWBC 231555
PMDEPD

EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1155 AM EDT FRI JUN 23 2017

VALID 12Z MON JUN 26 2017 - 12Z FRI JUN 30 2017

...PATTERN OVERVIEW/MODEL EVALUATION AND PREFERENCES...

THE MEDIUM RANGE PERIOD BEGINS MONDAY WITH A SYNOPTIC SCALE UPPER
LEVEL TROUGH OVER THE EASTERN U.S. AND AN UPPER LEVEL RIDGE OVER
THE INTERMOUNTAIN WEST AND DESERT SOUTHWEST. AN UPPER LOW OVER
BRITISH COLUMBIA AND SHORTWAVE ENERGY PIVOTING AROUND IT WILL
BEGIN TO WEAKEN THE WESTERN U.S. RIDGE BY TUESDAY WITH LOWERING
HEIGHTS ACROSS THE NORTHWEST THROUGH THE REST OF THE WEEK. THE
TROUGH ACROSS THE EAST IS FORECAST TO LIFT OUT AND LEAVE MORE OF A
ZONAL FLOW PATTERN BY THE MIDDLE TO END OF NEXT WEEK.

REGARDING THE EASTERN U.S. TROUGH...THERE REMAINS SOME MINOR
TIMING/SPEED DIFFERENCES BEGINNING DAY 4 WITH THE OPERATIONAL 06Z
GFS SLIGHTLY FASTER THAN THE REST OF THE GUIDANCE/ENSEMBLES. THE
00Z UKMET AND THE ENSEMBLE MEANS PROVIDES A NICE MIDDLE GROUND
SOLUTION SO THE WPC PREFERENCE FOR THIS SYSTEM WAS THE LATEST RUNS
OF THE GFS/ECMWF/UKMET THROUGH DAY 5...WITH DECREASING WEIGHTING
OF THE OPERATIONALS AND INCREASING WEIGHT TOWARDS THE EC MEAN AND
THE GEFS BY DAYS 6 AND 7.

OUT WEST...THE LATEST RUN OF THE GFS CONTINUES TO ADVERTISE A
FASTER AND MORE AMPLIFIED TROUGH AFTER DAY 5/WEDNESDAY AS IT
PROGRESSES ACROSS THE ROCKIES AND INTO THE PLAINS. THE 00Z GEFS
AND THE LATEST OPERATIONAL AND ENSEMBLE RUNS OF THE ECMWF OFFER A
SLOWER AND A BIT FLATTER PATTERN...WHICH ALSO AGREES WITH PREVIOUS
SHIFT WPC CONTINUITY. THIS CYCLE OF THE WPC PROGS USED AN EQUAL
BLEND OF THE 06 GFS/00Z ECMWF AT THE BEGINNING OF THE WEEK...WITH
INCREASING WEIGHTING TOWARDS THE ENSEMBLE MEANS BY THE END OF THE
WEEK.


...SENSIBLE WEATHER HIGHLIGHTS...

A LINGERING FRONTAL BOUNDARY NEAR THE GULF COAST AND OVER FLORIDA
SHOULD KEEP MAINLY DIURNALLY DRIVEN SHOWERS AND THUNDERSTORMS IN
THE FORECAST THROUGH MUCH OF THE WEEK. AND THE SURFACE HIGH
PRESSURE NORTH OF THE FRONT SHOULD PROMOTE A PERIOD OF LOW LEVEL
UPSLOPE FLOW AND POTENTIAL CONVECTIVE ENHANCEMENT ALONG THE
EASTERN SLOPES OF THE SOUTHERN ROCKIES AND ADJACENT WESTERN HIGH
PLAINS. LOWERING HEIGHTS ACROSS THE NORTHWEST WOULD MEAN INCREASED
POTENTIAL FOR RAIN AND CONVECTION ACROSS THIS REGION. ITS BY
MID-WEEK WHEN THIS UPPER LOW DROPS SOUTHWARD INTO SOUTH-CENTRAL
CANADA...DRIVING THE SURFACE FRONT EASTWARD INTO THE
PLAINS...WHERE CONFIDENCE CONTINUES TO INCREASE FOR GREATER
COVERAGE AND INTENSITY OF CONVECTION SPREADING ACROSS THE PLAINS
AND THE UPPER MIDWEST.

AS THE RIDGE BREAKS DOWN OUT WEST...TEMPERATURES SHOULD FINALLY
BEGIN TO MODERATE HEADING INTO NEXT WEEK...ALTHOUGH ANOMALIES MAY
STILL BE SLIGHTLY ABOVE NORMAL. THE FIRST HALF OF THE WEEK ACROSS
THE EASTERN U.S. SHOULD BE RATHER PLEASANT WITH DRY CONDITIONS AND
TEMPERATURES MAYBE AS MUCH AS 5 TO 10 DEGREES BELOW AVERAGE. BY
THE END OF THE WEEK...WITH SOUTHERLY FLOW INCREASING AHEAD OF THE
APPROACHING FRONT...EXPECT TEMPERATURES TO BOUNCE BACK TO NORMAL.


SANTORELLI

$$





USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.