Area Forecast Discussion
Issued by NWS Tucson, AZ

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000
FXUS65 KTWC 230929
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
230 AM MST SUN NOV 23 2014

.SYNOPSIS...A WEATHER SYSTEM PASSING NORTH OF THE AREA WILL GENERATE
GUSTY WINDS THIS AFTERNOON...MAINLY EAST OF TUCSON. THIS...ALONG
WITH A SECOND SYSTEM BRUSHING BY TO OUR NORTH MONDAY WILL COMBINE TO
USHER IN COLDER OVERNIGHT LOWS TONIGHT INTO WEDNESDAY.  HIGH
PRESSURE WILL BRING A STRONG WARMING TREND THE SECOND HALF OF THE
WEEK WITH A RATHER MILD THANKSGIVING.

&&

.DISCUSSION...DRY NORTHWESTERLY FLOW WITH MARKED WARMING IN THE MID
LEVELS OVER THE PAST 24 HOURS. THIS TREND WILL REVERSE TODAY AS AN
IMPULSE BRUSHES BY JUST NORTH AND EAST OF OUR AREA...USHERING IN
ANOTHER SHOT OF COOL AIR. THIS WILL IN TURN BRING COLDER OVERNIGHT
LOWS TONIGHT INTO MONDAY MORNING WITH A RETURN OF FREEZE AND HARD
FREEZE TEMPERATURES TO COLDER VALLEY LOCATIONS. ANOTHER IMPULSE WILL
CARVE DOWN THE AMPLIFYING EASTERN PACIFIC RIDGE MONDAY...BRINGING US
A REINFORCING SHOT OF COOLER AIR SPILLING OVER FROM NEW MEXICO. THE
POTENTIAL OF THE AIRMASS MONDAY NIGHT INTO TUESDAY MORNING IS THE
COLDEST OF THE SEASON...BUT MAY BE MITIGATED BY AN ENHANCED LOW
LEVEL EASTERLY GRADIENT RETURN FLOW IN EASTERN AREAS.

THE BOTTOM LINE IS THE NEXT 3 NIGHTS WILL BE ON THE COLD SIDE WITH
THE POTENTIAL FOR ONE OF THOSE TO BRING THE FIRST WIDESPREAD FREEZE
OF THE SEASON TO EASTERN PIMA COUNTY (INCLUDING METRO TUCSON). RIGHT
NOW MONDAY NIGHT INTO TUESDAY MORNING LOOKS LIKE THE BEST CHANCE FOR
THAT. AS MENTIONED...THE EASTERLY WINDS MAY TAKE THE EDGE OFF LOW
TEMPERATURES BUT ALL IT TAKES IS FOR THEM TO DIE OFF A FEW MINUTES
AROUND SUNRISE. AREAS THAT HAVE ALREADY SEEN FREEZES AND HARD
FREEZES WILL BE AT LEAST AS COLD AS THIS PAST WEEK. IT SHOULD BE
NOTED THAT THE GFS TYPICALLY DOES NOT HANDLE THE LOW END POTENTIAL
OF COLD AIR MASSES VERY WELL (AND IS CURRENTLY A LITTLE TOO
ENERGETIC AND PROGRESSIVE)...SO WE ARE BLENDING 00Z ECMWF/NAM WITH
EXTRA WEIGHT TO THE ECMWF FOR THE NEXT FEW NIGHTS.

RIDGE PHASING IN FROM THE EASTERN PACIFIC WEDNESDAY INTO
FRIDAY...BUT LOSING AMPLITUDE QUICKLY AS SIGNIFICANT ENERGY LINING
UP THROUGH THE PACIFIC SOUTH OF THE GULF OF ALASKA BEGINS TO EXERT
CONTROL AND SUBSUME MIDDLE AND HIGHER LATITUDE RIDGE STRUCTURE.
STILL LOOKING AT THE POTENTIAL OF A SIGNIFICANT WEATHER SYSTEM FOR
MOST OF WESTERN REGION DAYS 8-10.

&&

.AVIATION...VALID THRU 24/12Z.
PERIODS OF HIGH CIRRUS TO MOVE INTO THE REGION FROM THE NORTHWEST
THRU 24/12Z. SURFACE WINDS THRU 23/18Z GENERALLY LESS THAN 10 KTS
AND TERRAIN DRIVEN. THEN INCREASING W/NW WINDS 15 TO 25 KTS WITH
GUSTS TO 35 KTS EAST OF KTUS AND 10 TO 15 KTS GUSTING TO 20 KTS AT
KTUS/KOLS TERMINALS THRU 24/02Z. GENERALLY E/SE SURFACE WINDS
RELAXING OVERNIGHT TO LESS THAN 10 KTS. HOWEVER...STRONG NW WINDS AT
10 KFT OF 35 TO 45 KTS WILL PERSIST THRU 24/12Z. AVIATION DISCUSSION
NOT UPDATED FOR TAF AMENDMENTS.

&&

.FIRE WEATHER...GUSTY WEST TO NORTHWEST WINDS THIS AFTERNOON.
STRONGEST WINDS OF 20 TO 25 MPH WITH GUSTS TO 35 MPH ACROSS THE
TYPICALLY FAVORED UPPER GILA VALLEY. DAYTIME TEMPERATURES NEAR
NORMAL...HOWEVER FALLING DEWPOINTS WILL RESULT IN MIN RH VALUES
DROPPING INTO THE TEENS SUNDAY AND MONDAY AFTERNOONS. COMBINED WITH
GUSTY WINDS...POSSIBILITY EXISTS OF ISOLATED LOCATIONS BRIEFLY
APPROACHING RED FLAG CRITERIA IN AND AROUND SAFFORD THIS
AFTERNOON. MIN RH VALUES IN THE TEENS AGAIN MONDAY AFTERNOON.
HOWEVER WINDS WILL RELAX SOMEWHAT WITH GUSTS TO 20 MPH. WARMING
TEMPERATURES EXPECTED AFTER WEDNESDAY THRU THE END OF THE WEEK.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...NONE.

&&

$$

VISIT US ON FACEBOOK...TWITTER...YOUTUBE...AND AT WEATHER.GOV/TUCSON

MEYER/CARLAW/MEADOWS




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