Prognostic Meteorological Discussion
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578
FXUS01 KWBC 272048
PMDSPD

SHORT RANGE FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
447 PM EDT THU JUL 27 2017

VALID 00Z FRI JUL 28 2017 - 00Z SUN JUL 30 2017

...UNUSUAL JULY COASTAL STORM EXPECTED TO SPREAD SOAKING RAINS AND
GUSTY WINDS ACROSS THE MID-ATLANTIC FRIDAY AND SATURDAY...

...A THREAT OF FLASH FLOODING CONTINUES FOR PARTS OF DESERT
SOUTHWEST, CENTRAL/SOUTHERN ROCKIES INTO CENTRAL HIGH PLAINS...

THE STAGE IS SET FOR A RATHER UNUSUAL STORM TO FORM OVER THE
MID-ATLANTIC FRIDAY INTO SATURDAY.  THIS STORM, REMINISCENCE OF A
NOR`EASTER DURING THE COOL SEASONS RATHER THAN IN MID-SUMMER, IS
CURRENTLY AT ITS FORMATIVE STAGE ACROSS THE MID-MISSISSIPPI VALLEY
INTO OHIO VALLEY AS A COUPLE OF LOW PRESSURE WAVES RIDE ALONG A
COLD FRONT.  AS THE COOL AIR MASS BEHIND THE COLD FRONT CONTINUES
TO FILTER INTO THE NORTHERN U.S., AN UPPER-LEVEL TROUGH IS
FORECAST TO FORM OVER THE GREAT LAKES AND INTERACT WITH THE LOW
PRESSURE WAVES ALONG THE COLD FRONT.  THIS WILL LEAD TO THE
INTENSIFICATION OF A LOW PRESSURE SYSTEM OVER THE MID-ATLANTIC
REGION LATE FRIDAY INTO SATURDAY.  SHOWERS AND THUNDERSTORMS
CURRENTLY OVER THE MID-MISSISSIPPI AND OHIO VALLEYS ARE EXPECTED
TO SPREAD RAPIDLY EASTWARD ACROSS THE APPALACHIANS FRIDAY MORNING,
AND OVERSPREADING THE MID-ATLANTIC BY FRIDAY AFTERNOON.  THE STORM
IS FORECAST TO INTENSIFY MOST RAPIDLY FRIDAY NIGHT AND EARLY
SATURDAY AS IT MOVES ACROSS THE MID-ATLANTIC STATES.  RAIN IS
EXPECTED TO BECOME HEAVY FRIDAY NIGHT ALONG WITH STRONG GUSTY
WINDS, ESPECIALLY ALONG THE COAST.  POTENTIAL EXISTS FOR 2 TO AS
MUCH AS 5 INCHES OF RAIN TO FALL FROM THE CENTRAL APPALACHAINS
EASTWARD INTO THE NORTHERN MID-ATLANTIC COAST THROUGH SATURDAY.
THE STORM IS FORECAST TO REACH AN INTENSITY RARELY ATTAINED IN
LATE JULY ALONG THE EAST COAST OUTSIDE OF TROPICAL STORMS AND
HURRICANES.  HEAVY RAIN AND STRONG WINDS ARE EXPECTED TO LEAD TO
AREAS OF FLASH FLOODING ACROSS THE MID-ATLANTIC, ESPECIALLY NEAR
THE COAST, AS THE LOW PRESSURE CENTER COULD LINGER JUST OFF THE
COAST BEFORE IT SLOWLY WEAKENS BY SATURDAY EVENING.

PARTS OF THE DESERT SOUTHWEST, FOUR CORNERS, CENTRAL/SOUTHERN
ROCKIES AND INTO THE CENTRAL HIGH PLAINS WILL ALSO HAVE SCATTERED
SHOWERS AND THUNDERSTORMS AS MONSOONAL MOISTURE INTERACTS WITH A
WEAK FRONTAL BOUNDARY OVER THE WESTERN HIGH PLAINS.  IT APPEARS
THAT EASTERN COLORADO AND NEW MEXICO WILL GET THE GREATEST
RAINFALL TOTALS, WITH A FEW INSTANCES OF FLASH FLOODING POSSIBLE.
ACROSS THE SOUTHERN ROCKIES, MUCH OF THE INITIAL THUNDERSTORM
ACTIVITY SHOULD CONGREGATE ACROSS THE LOCAL MOUNTAIN RANGES BEFORE
MIGRATING TOWARD THE VALLEY FLOORS AND THE CENTRAL HIGH PLAINS.

MUCH OF THE HEAT OVER SOUTH-CENTRAL U.S. TODAY SHOULD GRADUALLY
ABATE AS THE AFOREMENTIONED COLD FRONT EDGES SOUTHWARD TOWARDS THE
GULF COAST.  THIS WILL CONFINE MUCH OF THE SHOWERS AND
THUNDERSTORMS ALONG THE GULF COAST THROUGH SATURDAY.  ELSEWHERE,
THE PACIFIC NORTHWEST SHOULD REMAIN DRY WITH NEAR NORMAL
TEMPERATURES.

KONG/HAMRICK


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