Analyzed 21Z Sun Jun 25, 2017
Valid 06Z Mon Jun 26, 2017
Valid 12Z Mon Jun 26, 2017
Valid 18Z Mon Jun 26, 2017
Valid 00Z Tue Jun 27, 2017
Valid 12Z Tue Jun 27, 2017
Valid 00Z Wed Jun 28, 2017
Valid 12Z Thu Jun 29, 2017
Valid 12Z Fri Jun 30, 2017
Valid 12Z Sat Jul 01, 2017
Valid 12Z Sun Jul 02, 2017
Valid 12Z Mon Jul 03, 2017
+ Short Range Forecast Discussion (Day ½-2½)
+ Medium Range Forecast Discussion (Day 3-7)
Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
425 PM EDT Sun Jun 25 2017
Valid 00Z Mon Jun 26 2017 - 00Z Wed Jun 28 2017
...Thunderstorms could be strong to severe from the southern
Rockies into the southern High Plains through tonight...
...The heat over the Pacific Northwest will abate by tomorrow...
...Much of the eastern two-thirds of the country will remain
cooler than normal for the next couple of days...
A broad trough aloft will continue to be the dominant feature over
the eastern two-thirds of the country for the next couple of days.
At the lower levels, a high pressure system, reminiscent of a
cold season arctic outbreak, is forecast to build southeastward
across the Plains and eastward into the East Coast during the next
couple of days. This will keep temperatures much cooler than
normal with mostly clear skies from the Plains eastward to the
East Coast, making for very pleasant conditions for late June.
Over the Great Lakes into New England however, disturbances
associated with reinforcing shots of cool air from Canada will
keep a good chance of showers and thunderstorms around through
Monday before tapering off gradually from west to east on Tuesday
as the broad upper trough weakens. The disturbances will also
help the formation of secondary cold fronts along the East Coast,
which is pretty unusual for late June.
Along the southern flank of the cool air mass, a stationary front
will linger from along the southeast U.S. coast down to the Gulf
Coast. The front will provide a focus for scattered showers and
thunderstorms, especially during the afternoon and evening. Near
the tail end of the front, thunderstorms could become severe
tonight from the southern Rockies of New Mexico into the adjacent
High Plains under an upper-level disturbance. Farther north,
scattered showers and storms are expected to form ahead of a
secondary front over the central Plains on Monday. The front, or
a weakness in the high pressure system, will push to the south and
east, bringing the storms farther down into the mid-Mississippi
Valley by Monday evening before spreading eastward into the East
Coast on Tuesday.
Out West, heat has been the story for the past couple of days over
the Pacific Northwest. A cold front from the eastern Pacific is
forecast to arrive tomorrow, bringing showers and thunderstorms
across the interior mountains into the northern Rockies, reaching
the northern High Plains by Tuesday. This will usher in the much
cooler marine air back into the Pacific Northwest, ending the
recent heat wave. Meanwhile, the northern and central Plains will
begin to see showers and thunderstorms forming near and ahead of a
warm front as a low pressure system is forecast to develop in the
northern High Plains.
Over the Desert Southwest, the heat will gradually abate day by
day. However, the recent extreme heat and dry conditions will
continue to increase fire danger in the area.
Graphics available at
+ Additional Links
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1056 AM EDT SUN JUN 25 2017
VALID 12Z WED JUN 28 2017 - 12Z SUN JUL 02 2017
...HEAVY RAIN POTENTIAL EXISTS FROM THE CENTRAL PLAINS TO THE
UPPER GREAT LAKES LATE THIS WEEK THROUGH THE WEEKEND...
***PATTERN OVERVIEW AND MODEL PREFERENCES***
THE MODELS CONTINUE TO SHOW A SIMILAR LARGE SCALE PATTERN ON
WED-THU WITH A LEAD UPPER TROUGH PROGRESSING OUT OF THE UPPER MS
VALLEY TOWARDS THE UPPER GREAT LAKES THAT HAS POTENTIAL TO PRODUCE
A ROUND OF HEAVY SHOWERS/STORMS. BOTH THE GFS AND ECMWF SHOW
DIFFERENCES FROM RUN TO RUN AND WITH EACH OTHER...AS WELL AS
DIFFERENCES WITH THEIR ENSEMBLE MEANS. AN EQUALLY WEIGHTED
FORECAST WAS USED AMONG BOTH THE OPERATIONAL AND MEANS UNTIL
BETTER AGREEMENT DEVELOPS. THE 06Z GFS WAS A SLOW OUTLIER SO THE
00Z RUN WAS USED INSTEAD.
ON THU-FRI...THE INITIAL LEAD WAVE CROSSES THE GREAT LAKES INTO
SOUTHEAST CANADA WITH THE FRONT EXTENDING ACROSS NORTHERN NEW
ENGLAND. THE BETTER OVERLAP WITH THE MEANS FROM THE GEFS AND
ECMWF LED TO THESE SOLUTIONS TO PLACE LOW PRESSURE AND THE FRONTAL
THE MODELS/ENSEMBLES SHOW A WAVE ROTATING AROUND THE CLOSED LOW
MOVING EAST FROM ALBERTA...WITH THE WAVE PROGRESSING ACROSS THE
NORTHERN PLAINS FRI TO THE UPPER MS VALLEY AND UPPER LAKES SAT.
THIS WAVE SPURS DEVELOPMENT OF A WAVE OF LOW PRESSURE ALONG THE
FRONT ROUGHLY IN KS THU TO EASTERN IOWA FRI AND ACROSS LOWER MI
FRI NIGHT TO ONTARIO SAT MORNING. ANOTHER ROUND OF HEAVY
SHOWERS/STORMS IS POSSIBLE WITH THIS WAVE. WITH THIS WAVE THE 00Z
ECMWF BROKE CONTINUITY BY HAVING A HIGHER AMPLITUDE SHORTWAVE AND
DOWNSTREAM RIDGE...FORCING LOW PRESSURE TO BE FURTHER WEST THAN
THE PRIOR 12Z RUN AND 00Z ECMWF ENSEMBLE MEAN/GFS/GEFS MEAN. A
LITTLE MORE WEIGHTING WAS GIVEN THE GEFS MEAN/ECMWF MEAN AND LESS
TO THE OPERATIONAL ECMWF AND GFS GIVEN THEIR OPERATIONAL
VARIABILITY RUN TO RUN.
ACROSS THE WESTERN US...THE AFOREMENTIONED WAVE MOVING EAST ACROSS
THE NORTHERN ROCKIES AND PLAINS WILL SUPPRESS THE UPPER LEVEL
RIDGE SOUTHWARD INTO MEXICO. BY NEXT WEEKEND, UPPER LEVEL
TROUGHING DOWNSTREAM FROM A CLOSED LOW OVER THE NORTHERN PACIFIC
WILL MOVE ONSHORE AND INLAND...WITH LOW PRESSURE DEVELOPING ON THE
PLAINS DAY 7 SUN 02 JULY. THE 00-06Z GFS WERE ON THE HIGHEST
AMPLITUDE SIDE OF THE GUIDANCE DISTRIBUTION OF THE 500 MB
WAVE...SO MORE WEIGHTING WAS GIVEN TO THE 06Z GEFS MEAN/00Z ECMWF
ENSEMBLE MEAN AND 00Z ECMWF. ADDITIONAL RAINFALL WILL DEVELOP IN
THE CENTRAL PLAINS TO UPPER MS VALLEY...WHICH COULD BE A PROBLEM
IF RAINFALL OCCURS IN AREAS IMPACTED FROM THE PRIOR WAVES CROSSING
THE MULTIPLE WAVES OF LOWER HEIGHTS/PRESSURE CROSSING FROM THE
CENTRAL PLAINS TO UPPER MS VALLEY AND UPPER GREAT LAKES SHOULD
PRODUCE AT LEAST A COUPLE OF ROUNDS OF HEAVY SHOWERS/STORMS.
SIGNIFICANT FLOODING POTENTIAL IS POSSIBLE IF THERE IS OVERLAP OF
BOUTS OF SHOWERS AND STORMS. THIS WILL BE WATCHED CLOSELY DUE TO
MULTI-DAY TOTALS OF SEVERAL INCHES OF RAIN POSSIBLE FROM EASTERN
KANSAS AND NEBRASKA ACROSS NORTHERN MISSOURI AND IOWA TO NORTHERN
ILLINOIS...INCLUDING THE CHICAGO AREA. AREAS OF EXCESSIVE
RAINFALL CAPABLE OF PRODUCING FLASH FLOODING APPEAR INCREASINGLY
THE SUCCESSION OF UPPER TROUGHS CROSSING THE UPPER MS VALLEY AND
UPPER LAKES SHOULD HELP KEEP TEMPERATURES WELL BELOW NORMAL
THROUGH NEXT WEEKEND...WITH ANOMALIES NEAR 10 DEGREES BELOW NORMAL
RECURRING IN AREAS NEAR LAKE SUPERIOR IN THE ARROWHEAD OF MN TO
THE KEWEENAW PENINSULA/ UPPER PENINSULA OF MICHIGAN.
ANOMALIES SHOW FORECAST HIGH TEMPERATURES SLIGHTLY ABOVE AVERAGE
IN THE SOUTHWEST AND SOUTHERN GREAT BASIN TO THE SOUTHERN
ROCKIES...WITH AREAS OF 3-5 DEGREES ABOVE THE 30 YEAR MEAN
TEMPERATURES EXPECTED THROUGH THE WEEKEND. A WARM STRETCH IS ALSO
EXPECTED OVER THE MID ATLANTIC STATES LATER THIS WEEK THROUGH THE
WEEKEND...WITH 3-5 DEGREES ABOVE NORMAL COMMON.