Fire Weather Outlook Day 1


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FNUS21 KWNS 211648
FWDDY1

Day 1 Fire Weather Outlook  
NWS Storm Prediction Center Norman OK
1147 AM CDT Mon May 21 2018

Valid 211700Z - 221200Z

...CRITICAL FIRE WEATHER AREA FOR EASTERN ARIZONA AND FAR WESTERN
NEW MEXICO...

...Arizona, western New Mexico, southeastern Utah, and far
southwestern Colorado...
Moist easterly-southeasterly surface flow developed farther west
than previously anticipated over western New Mexico. Thunderstorms
are expected to develop by early afternoon over western New Mexico 
with building cumulus already apparent on visible satellite imagery
over far western New Mexico. Deeper boundary layer moisture should
help produce wetting rainfall thus limiting the eastern extent of
dry thunderstorms. The scattered dry thunderstorm area was removed,
and the eastern extent of the isolated dry thunderstorm area was
moved farther west to reflect the increase of moisture and
thunderstorm coverage now expected. 

Precipitable water values of 0.4-0.8" are observed/forecast in
western New Mexico, which should keep initial thunderstorm
development drier. However, the latest CAMs guidance shows storms in
western New Mexico growing upscale fairly quickly and becoming
wetter and outflow dominant. Outflow boundaries and terrain features
should continue the development of thunderstorms throughout the
afternoon/evening. It's also possible in far western New Mexico that
a second round of thunderstorms develop late afternoon/early evening
as heights fall and enough residual moisture remains. 

Critical fire weather conditions are expected to develop this
afternoon/evening across eastern Arizona and far western New Mexico
with forecast single-digit values of RH and sustained southerly
winds of 15-25 mph. The Critical delineation was extended farther
east over western New Mexico as the mid-level trough is forecast to
move quicker than previously forecast. Additionally, parts of far
western New Mexico could see lightning followed by dry and windy
conditions reaching critical thresholds.

..Nauslar/Karstens.. 05/21/2018

.PREV DISCUSSION... /ISSUED 0147 AM CDT Mon May 21 2018/

...Synopsis...
Fire weather concerns will be concentrated across parts of Arizona,
New Mexico, and vicinity this afternoon as a cut-off mid-level low
migrates southeastward across California.  Enhanced (40-50 kt)
mid-level flow will extend eastward from this low from Baja
California northeastward into Arizona and western New Mexico
throughout the forecast period.  At the surface, a weak trough
across the Lower Colorado River Valley will encourage southerly flow
across the region, and a second area of troughiness in far west
Texas will encourage robust low-level moist advection across
portions of central New Mexico.

...Arizona, New Mexico, far southwestern Colorado, and far southern
Utah...
By mid-afternoon, insolation amidst continued dry conditions across
Arizona and far western New Mexico will result in warm surface
temperatures (70s to 80s F) and critically low RH values (3-15%). 
Additionally, models suggest areas of 20-30 mph southerly surface
flow especially across eastern Arizona and far western New Mexico. 
A critical fire weather delineation remains in place where surface
winds are most likely to meet critical thresholds (20+ mph for three
hours or more) amidst the dry surface conditions.  An elevated fire
weather delineation also surrounds the critical area where <15% RH
values will exist but wind speeds will exceed critical thresholds on
a brief/localized basis.  

Farther east (from western into central New Mexico), moist advection
was occurring and will continue through the afternoon.  Surface
heating within this increasingly moist airmass will result in
widespread thunderstorm activity developing perhaps as early as
around 16-17Z/10-11a MDT across western New Mexico - expanding
across the remainder of the state over the course of the afternoon. 
Thermodynamic profiles support occasional lightning strikes, and
40-50 kt mid-level flow will encourage storm movement/propagation
and limit the amount of wetting rainfall in any given area -
especially across northwestern New Mexico displaced from the most
pronounced moist advection.  Precipitable water values should remain
the lowest (around 0.5 inch) for much of the afternoon across the
scattered dry thunderstorm area, and this area will contain the
greatest potential for dry lightning strikes.  Farther south toward
south-central New Mexico, PW values will likely approach 1 inch and
limit dry lightning to strikes occurring on the periphery of wetting
thunderstorm cores.  These thunderstorm areas may need to be
reconfigured later today pending observational trends.

...Please see www.spc.noaa.gov/fire for graphic product...

$$


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