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Area forecast discussion 
National Weather Service North Platte NE 
302 PM CST Thursday Jan 8 2009 


..forecast challenges are wind potential and temperatures with frontal passage 
tomorrow...then temperatures in the extended and the magnitude of 
the deep freeze next week... 


Discussion... 


Near term...tonight through Sunday night...main forecasting 
challenge over the next 36 hours is the timing of the frontal passage on 
Friday and wind potential behind the front Friday afternoon. The 
front is expected to enter the northern portion of the County Warning Area around 
12z tomorrow morning...exiting the County Warning Area by 15z. The main surge of 
cold air will trail the front some...so have incorporated an 
atypical diurnal temperature curve for tomorrow with morning highs 
in the north and midday highs in the south. As cold advection 
increases tomorrow afternoon...winds will increase accordingly. 
BUFKIT soundings...forecast 850 mb winds and numerical guidance wind 
speeds tomorrow afternoon are borderline for Wind Advisory 
criteria...and will let the night crew take a further look when the 
new model guidance comes in this evening. Not overly impressed in 
wind potential tomorrow afternoon as 850 mb winds are generally 30 to 
40 kts across the County Warning Area. Would like to see these in the 40 to 50 knots 
range before pulling the trigger on a Wind Advisory at this time. 


The Arctic air mass will move quickly east as high pressure builds 
into the Ozarks Saturday. Southwesterly winds will push temperatures into 30s and 
40s for both Saturday and Sunday. Have retained low probability of precipitation in the 
forecast across the northwest for Sunday...as a decent jet streak 
approaches from the northwest. Additional middle level forcing noted 
there along with northwesterly winds off the Black Hills which 
favors precipitation over the far northwestern zones. Not expecting much in 
the way of quantitative precipitation forecast as top down saturation is expected. 


Long term...Monday through Thursday...the models are coming into 
better agreement today...with what appears to be a fairly 
significant Arctic outbreak next week. As mentioned earlier this 
morning by Gid in the chat...temperatures across the alaskan interior were 
running 30 degree below normal this morning with readings of 50 to 60 
below zero. This airmass is expected to modify significantly as it 
heads south early next week. A 1050+ mb high will transport the bulk 
of this Arctic air...at least the portion which stands to impact western 
and northern nebr the greatest...on Thursday. Without snowcover 
present across the area and none expected through this time...a 
conservative estimate is to shave off 20 degrees from climatology for 
highs and lows for Thursday. Since there are still a little 
uncertainty with where the core of this Arctic air tracks across 
the Continental U.S....will start with a 10 degree cut off of climatology. This seems 
to agree with the neighbors at this time. If model trends stay on the same 
track the next several days...we could be looking at highs in the 
single digits and teens late next week and lows at or below zero. 
Thankfully we are lacking snow cover right now...or we would be 
looking at the potential of below zero highs in some locations. 


&& 


Aviation... 
middle and high cloud decks will continue to drift over western and 
north central Nebraska overnight into early Friday leaving VFR 
conditions in place. A front will move quickly southward through the 
day Friday with a secondary shot of cold air coming in the 
afternoon. This should bring in lower cloud deck and chance of very 
light precipitation or flurries. VFR conditions are forecast for 
kvtn/klbf tafs behind the frontal passage though some MVFR conditions may be 
possible across northern Nebraska in the afternoon but confidence 
not high enough to introduce at this time. Winds will be larger concern for 
light aircraft on Friday as north/northwest wind increase to 25 to 
35 miles per hour along and behind the front as cold air spills southward. 


&& 




Lbf watches/warnings/advisories...none 


$$ 


Short and long term...buttler 
aviation...Phillips