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954
FXUS65 KRIW 230932
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
332 AM MDT WED JUL 23 2014

.SHORT TERM...TODAY THROUGH FRIDAY NIGHT

WV IMAGERY SHOWING ROBUST UPR RIDGE...SANDWICHED BETWEEN TWO UPR
TROFS... CENTERED OVER CO AND EXTENDING ACROSS THE CWA TONIGHT WITH
THE DIRTY PORTION OF THE RIDGE TO THE NORTH IN MT AND AROUND THE
HORN INTO SD AND NE...LEAVING THE FA DRY.

THRU THE FCST PERIOD...THE THE MEAN POSITION OF THE CENTER OF THE
UPR HIGH WILL NOT CHANGE MUCH....ONLY TRENDING SWD FROM CO INTO THE
NM/AZ REGION. HOWEVER...THE N/S EXTENT OF THE HIGH WILL GET SQUASHED
BY DAY 3 AS THE WRN COASTAL TROF PUSHES ACROSS SRN CA...DECREASING
HEIGHTS OVR WY ALONG WITH TEMPERATURES...GIVING A BRIEF RESPITE TO
AN OTHERWISE VERY HOT FCST THRU THURSDAY. LEADING EDGE OF WEAK SW
EMBEDDED IN THE PERIPHERY OF UPR HIGH OVR AZ TONIGHT WILL ROTATE
CLOCKWISE ACROSS THE FA BY THIS EVENING...GIVING SLIGHT CHANCES FOR
CONVECTIVE ACTIVITY WITH LITTLE RAIN...BUT A LITTLE DRY LIGHTNING
AND GUSTY ERRATIC WINDS POSSIBLE...OVR MAINLY THE SRN AND SERN
PORTION OF THE FORECAST AREA...IF A STORM CAN GO AT ALL WITH H7
TEMPS WARMING TO BETWEEN 17 AND 19 DEG C. OTHERWISE...A LITTLE
STRONGER SW WILL SWING THRU THE NWRN FA THU MORNING AROUND THE NW
CONUS TROF OFFERING SLIGHTLY BETTER INSTABILITY EVEN IN THE EARLY
MORNING HOURS WITH INCREASED LAPSED RATES UNDER A COOLING MID/UPR
LVL. BY AFTERNOON THU...THIS DISTURBANCE WILL COMBINE WITH SOME
MONSOONAL MOISTURE ACROSS S AND ERN WY...OFFERING ANOTHER CHANCE FOR
CONVECTION...BUT MOSTLY ONLY THE FAR SRN AND ERN PORTIONS OF THE CWA
WILL HAVE ANY CHANCE FOR CONVECTION...NEAR DEVELOPING LEE SIDE SFC
LOW AND FRONT. FRIDAY WILL BE A BIT COOLER THAN THE PREVIOUS TWO
DAYS...AND DRIER AND MORE STABLE TOO...WITH VIRTUALLY NO CHANCE FOR
ACTIVE CONVECTION EXCEPT FOR POSSIBLY NEAR THE WY/CO BORDER. MORE
SIGNIFICANTLY...AND IN ADDITION TO THE ISOLATED THUNDER MENTIONED
ABOVE...WILL BE THE INCREASED FIRE DANGER THAT WILL DEVELOP ACROSS
THE SRN AND ERN ZONES. BEGINNING TODAY AND LASTING THRU FRI...HOT
DAYTIME TEMPS IN THE 90S WILL COMBINE WITH LOW RH VALUES RANGING
FROM THE UPR SINGLE DIGITS TO THE MID TEENS AND INCREASING SW WINDS
ACROSS AREAS THAT HAVE RECENTLY SEEN DRY FUEL STATUS GO CRITICAL.
WHILE TODAY WILL BE A MARGINAL RED FLAG DAY AS FAR AS WINDS AND RH
GO...THE ADDITION OF POSSIBLE ISOLATED THUNDER RAISE ENOUGH CONCERNS
TO START THE WARNING TODAY. THEN BY THURSDAY...BOTH THE SURFACE
PRESSURE FIELDS ALONG WITH INCREASED UPR FLOW IN RESPONSE TO THE
PASSING OF THE UPR WAVE AND DEVELOPING LEE LOW WILL BOTH INCREASE
THE LOCAL P GRAD AND BRING WIND DOWN FROM ALOFT INTO A WINDY
CATEGORY OVR THE CENTRAL...SOUTHERN AND EASTERN FA. SIMILAR
CONDITIONS WILL BE PRESENT FRIDAY EVEN WITH COOLER HIGH TEMPS
AROUND. HAVE EXTENDED THE RFW ACCORDINGLY SO THAT THE WARNING WILL
NOW GO FROM NOON TODAY...THRU FRI EVENING. ADDITIONALLY...HAVE ADDED
A FIRE WEATHER WATCH FOR ZONE 276 (CODY FOOTHILLS) THAT WILL START
THURSDAY AT NOON AND ALSO RUN THRU FRI EVENING.

.LONG TERM...SATURDAY THROUGH WEDNESDAY

UPPER LOW DIVES SE ACROSS THE NORTHERN PLAINS SATURDAY AND CARVES
OUT LONGWAVE TROUGH ACROSS THE EASTERN U.S. BY MONDAY.  THIS WILL
ALLOW UPPER HIGH OVER THE SOUTHERN/CENTRAL ROCKIES TO PHASE WITH
RIDGE OVER CENTRAL CANADA...SETTING UP A BLOCKING PATTERN OVER NORTH
AMERICA WITH UPSTREAM TROUGH OVER THE EASTERN PACIFIC.  UPPER HIGH
OVER THE SW U.S. WILL RETROGRADE SLIGHTLY MON-WED.  BOTH GFS AND
ECMWF ENSEMBLE MEANS HAVE THIS UPPER HIGH CENTERED OVER AZ BY 00Z
THURSDAY WITH THE ECEM SLIGHTLY FURTHER WEST.  THIS WESTWARD SHIFT
WILL BRING A MORE UNSETTLED NW FLOW ACROSS WYOMING TUESDAY AND
WEDNESDAY.

SATURDAY...VERY DRY AIRMASS WILL REMAIN OVER THE REGION WITH
STATIONARY SURFACE FRONT ALONG THE EAST SLOPES OF THE DIVIDE...A
LIGHT UPSLOPE FLOW BEHIND THE FRONT.  BREEZY N-NW WINDS WILL REMAIN
ACROSS SW WYOMING THOUGH NOT AS STRONG AS FRIDAY...HOWEVER FIRE
WEATHER CONDITIONS WILL REMAIN ELEVATED TO EXTREME.

SUNDAY...CANADIAN SFC HIGH PRESSURE BUILDS INTO THE NORTHERN PLAINS
WITH HEAT SFC LOW OVER THE GREAT BASIN.  THIS WILL BRING E-NE FLOW
AND LIGHTER WIND ACROSS SOUTHERN WYOMING ALONG WITH A BIT HIGHER
RELATIVE HUMIDITY.  TEMPERATURES WILL BE A FEW DEGREES COOLER ACROSS
THE CENTRAL AND SOUTHWEST...WHILE TEMPS WILL LIKELY BE A FEW DEGREES
WARMER ACROSS THE WESTERN VALLEYS.

MONDAY THROUGH WEDNESDAY...THE "RING OF FIRE" BEGINS TO DEVELOP
AROUND FOUR CORNERS UPPER HIGH MONDAY WITH SUB-TROPICAL DISTURBANCES
ROTATING AROUND PERIPHERY OF HIGH NORTHWARD ACROSS THE GREAT BASIN
AND WESTWARD ACROSS WYOMING.  THIS WILL BRING AN INITIAL SURGE OF
SUB-TROPICAL MOISTURE ALONG WITH ISOLATED TO WIDELY SCATTERED
THUNDERSTORMS INTO THE WEST MONDAY AFTERNOON WITH SOME OF THIS
ACTIVITY SPREADING EAST OF THE DIVIDE LATE.  NW FLOW ALOFT WITH
LIGHT UPSLOPE E-NE SFC FLOW WILL SHIFT THE BEST MOISTURE AND
INSTABILITY ALONG AND EAST OF THE DIVIDE TUESDAY AND WEDNESDAY...A
SET UP THAT WILL BE FAVORABLE FOR A FEW STRONG TO SEVERE
STORMS.


&&

.AVIATION.../12Z ISSUANCE/

CONVECTION WILL BE HARD PRESSED TO DEVELOP TODAY...WITH A MAINLY
STABLE ATMOSPHERE DUE TO WARM MID LEVEL TEMPS...AND MEAGER MOISTURE.
HAVING SAID THAT THERE COULD BE SOME VERY ISOLATED CONVECTION OVER
THE MOUNTAINS THAT TRY TO FORM LATE THIS AFTERNOON AND EVENING.
CHANCES ARE TOO REMOTE TO MENTION AT ANY TAF SITE. WINDS WILL
GENERALLY BE LIGHT THROUGH THE MORNING...BECOMING BREEZY FROM THE
SOUTHWEST/WEST OVER THE WEST AND FROM THE WIND CORRIDOR FROM
KRKS-KCPR. WINDS MORE SOUTHERLY IN JACKSON HOLE.

&&

.FIRE WEATHER...

A RED FLAG WARNING IS IN EFFECT FOR PORTIONS OF CENTRAL AND SOUTHERN
WYOMING FROM NOON TODAY THROUGH FRIDAY EVENING. A FIRE WEATHER
WATCH IS IN EFFECT  FOR THE CODY FOOTHILLS FROM NOON ON THURSDAY
THROUGH FRIDAY EVENING. CRITICAL FIRE WEATHER CONDITIONS WILL
DEVELOP ACROSS AREAS WITH CRITICALLY DRY FUELS BEGINNING THIS
AFTERNOON...AS HOT DAYTIME TEMPERATURES IN THE 90S COMBINE WITH LOW
RH VALUES RANGING FROM THE UPR SINGLE DIGITS TO THE MID TEENS AND
INCREASING SOUTHWEST TO WEST WINDS. ADDITIONALLY...THE POSSIBILITY
OF ISOLATED THUNDER TODAY ALSO REINFORCES THIS DECISION. THURSDAY
WILL PERHAPS SEE THE MOST EXTREME BEHAVIOR AS A STRONGLY INCREASED
SURFACE PRESSURE GRADIENT COMBINES WITH STRONGER UPPER LEVEL FLOW TO
GIVE WESTERLY WINDS THAT WILL GUST BETWEEN 25 AND 35 MPH IN THE
AFTERNOON AND EARLY EVENING. SIMILAR CONDITIONS WILL BE PRESENT
FRIDAY...ALTHOUGH HIGH TEMPERATURES WILL BE A BIT COOLER. HAVE ALSO
ADDED A FIRE WEATHER WATCH FOR ZONE 276 (CODY FOOTHILLS) THAT WILL
START THURSDAY AT NOON AND ALSO RUN THRU FRIDAY EVENING FOR SIMILAR
REASONING.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
RED FLAG WARNING FROM NOON TODAY TO 9 PM MDT FRIDAY
WYZ279-280-283-285-287-300.

FIRE WEATHER WATCH FROM THURSDAY AFTERNOON THROUGH FRIDAY
EVENING WYZ276.

&&

$$

SHORT TERM...BRAUN
LONG TERM...AEM
AVIATION...WM
FIRE WEATHER...BRAUN








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